BIOLOGY-TOPIC GROWTH

GROWTH

GROWTH

Growth is an irrevessible increase/permanent increase in size and mass of an organisim

Development

Development are changes in the complexity/structure of an organism

· It involves differentation and formation of various tissue that perform specialized functions.

· Growth is quantitative (can be measured: height, mass,volume

· Development is qualitative (can’t be measured)

· The growth and development of a young organism into adult involves cell division (multiplication of one cell into two, two into four and four into eight ect.

· The newly formed daughter cell have the same composition as the parent cell although they may be smaller, late cells enlarge to the adult size and even divide again.

CONCEPT OF GROWTH

Growth can be measured using a curve. A growth curve is a graph obtained when data collected during stages of growth is plotted against the time.

A growth curve shows growth pattern of the organism. In most organisms growth pattern is almost the same where by first shows slow then speeds up and finally slows down.

This pattern gives an S-shaped curve known as sigmoid curve.

Lag phase

Lag phase is a period when the rate of growth is very slow during the stage the number of cell dividing through mitosis are few

Log phase /exponential phase

This phase involves very rapid growth where by the number of cell division is higher than the dead face

Linear growth /declarating phase.

This phase involves the decline in the rate of growth as maturity is approached the rate of cell division decrease.

Stationary phase/plateau phase

This phase marks the period of no further changes in the size of the organism the organism has sustained maturity new cells are formed only to replace those worn out or dead cells

Measurement of growth

1. Measuring the length parts used to measure growth leaves, stems, internodes etc.

2. Measuring weight

3. Measuring area

MITOSIS AND GROWTH

Mitosis is a type of cell division which increases the number of cells which bring about growth.

· It results into two identical daughter nucles with a diploid number of chromosomes

Phases of Mitosis

· It consists of 5 phases namely

§ Interphase

§ Prophase

§ Metaphase

§ Anaphase

§ Telophase

1. INTERPHASE

o This is the phase were the cell is engaged in many cellular activities to prepare for the cell division.

o The entire proces takes about 1hour. It is incorrectly referred to as resting phase.

o The following are observed

§ DNA replicates

§ Chromosomes apper

§ Centriole replicates

§ Energy is synthesised and stored

2. PROPHASE

o In this stage centrioles separate and migrate to opposite cell’s poles.

o Chromosomes become visible, thichen and shorten

o Each chromosome divides into two along its length replication except at the centromere. Chromosomes now called chromatids.

o The nucleas membrane and nucleolus gradually disappears.

o A network of fibres starts to form

3. METAPHASE

· The chromatids move to the centre of cell.

· The chromatids become arranged and attached to spindle fibres by centromeres.

· The chromatids draw apart at the centromere region

4. ANAPHASE

· In this stage, after the sister chromatids part company, they migrate to the apposite poles of the spindle, the centromere leading it.

· Chromatids reach their destination towards the poles of the spindle. Now chromatids are called chromosomes.

5. TELOPHASE

· In early telophase, the spindle fibres disappear,

· A nuclear membrane is formed enclosing the newly formed chromosomes.

· At this stage, in animal cells, the cell starts to construct across the middle into two new cells.

· In plant cells a cell wall is formed across the middle of the cell

SYTOKINESIS

This is the division of the sytoplasm

· It is through the formation of a new cell wall in plant cell or the constriction of the animal cell.

SIGNIFICANCE OF MITOSIS

· It is the basis of asexual reproduction

· It maintains the diploid state of the organism

· It is the basis of growth i.e it brings about growth in terms of increase in number of cells.

· It help to recovery of dead worn out cell

DIFFERENCE BETWEEN MEIOSIS AND MITOSIS

MEIOSIS

MITOSIS

Occurs in reproductive cells to form gameters

Occurs in body cells during grow and tissue repair (somatic cell)

Gametes fuse to form a zygote

New cells do not fuse to form a zygote

Variation occurs through chromosomes recombination

No variation, all are like parents.

Takes place in two phases to complete

Take place in one phase to complete a successful cell division

New formed daughter cells are in haploid state

Newly formed daughter cells are in diploid state

THE PROCESS OF GROWTH

It in volves the following: -

§ Assimilation

§ Cell division

§ Cell expansion

1. ASSIMILATION

· Is the incorporation of the materials absorbed from the surrounding into the cell metabolism (food and gases)

· From this procces cell get raw material for energy production.

· Energy is used in the next stage

2. CELL DIVISION

· This is the division of cell nucleas and cytoplasm

· It results in increase in the number of cells (growth)

3. CELL EXPANSION

· Cell increase in size when they absorb water by osmosis. The cell take in water in their vacoules and expand.

GROWTH AND DEVELOPMENT IN ANIMALS

TYPES OF GROWTH

1. ALLOMETRIC GROWTH

Is the type of growth where by different parts of the body of an organism grow at different rates and stop growing at different rates.

2. DIFFUSE GROWTH

Is the type of growth where by growth occurs all over the body of an organism

3. LOCALIZED GROWTH

Is the type of growth where by growth occurs in certain region e.g: In plants at the tip and shoots of the roots. Tips are called maristems

4. INTERMITTENT GROWTH

Is the type of growth in intropods which growth takes place isnseries of stages called instars. Example in insects an egg hatch into larva then develops into a pupae, finally an adult.

5. ISOMETRIC GROWTH

Is the type of growth where by all body organs grow at the same rate e.g in a fish.

6. DETERMINATE GROWTH

This growth is seen in individuals which stop growing when certain body size or age is attained e.g. in mammals, birds, animals, plant

7. INDETERMINATE GROWTH

Is the type of growth shown by organisms that do not stop to grow i.e organism show increasing growth

Example in shrubs, corals, fish, reptilires

GROWTH AND DEVELOPMENT IN ANIMALS

Growth in arthropods

At arthropods show discontinuous growth. This is a type of growth characterized by a number of periods of rapid growth followed by periods of little or no growth.

Some arthropods they show incomplete life style also there some arthropods show complete life cycle are known as polometabolous I.e.Butter flies, house flies. Bittles, etc.

INTERMITTENT GROWTH

This is the type of growth that occurs in a series of stages in arthropods. These series of stages show sudden changes in weight or length measured over weeks or months.

Each stage is known as instars. All arthropods have an exo –skeleton which prevents overall growth of the body.

Therefore they have to shade their exo skeleton so that they can grow this is known as moulting or ecoysis.

At the final shading of the exoskeleton the insect under goes full development and the wings expand enabling flight

METAMORPHOSIS

It is the changes in the body shape and the structure in the life cycle and structure of insects and amphibians.

It occurs in a series of stages depending on the number of stages.

They are divided in two stages

1. In Complete metamorphosis

2. Complete metamorphosis

Incomplete metamorphosis

These growth occur in amphibia and some insect where by a growth pass into three stage which is from egg, nymph to adult.The egg hatch into nymph which resembles the adult only if smaller in size most of the time it doesn’t have wings

Nymph grows and mould many times before the adult emerges.

Stages of incomplete metamorphosis

Examples in amphibians

· Frog

· Toad etc

Complete metamorphosis

Insects such as: Butterflies, house flies, mosquitoes, moths, etc.

They show complete metamorphosis. The eggs laid by adults hatch into lava which is completely different in form and behavior from the adult.

Lava is the feeding and growing stage after which is transformed into pupa depending on the insect spices a larva is referred to as a grub maggot or caterpillar.

A pupa is outwardly dormant but inside there is a lot of development such as cell division and cell differentiation of body organs until mature or imago organism emerges

FACTORS THAT REGULATE GROWTH

1. Density

2. Food and water

3. Accumulation of toxic waste

4. Diseases

5. Climate

6. Oxygen and carbon dioxide

7. Predators and parasites

8. Psychological factors

HUMAN POST NATAL GROWTH AND DEVELOPMENT

1. Child hood or infancy [0-12 years]

2. Adolescence [11-14years]

3. Adult hood [14/16- 45 years]

4. Old /senescence [ 45 and above ]

5. Death

1. CHILD HOOD

This is the stage between birth and sexual maturity. After the delivery umbilical code is tightened and cut using a sterilized equipment then the body has to be wiped with a cloth dipped in warm water.

Then it has to be dressed up in clean lose fitting cloths the baby cloths and napkins should be made of cotton or soft woolen fabrics. The baby has to be provided with breast milk which contains almost all the nutrients .

The production of milk by mammary glands is called lactation. The lactation is controlled by proclacting hormone. The milk produced in the first days after delivery is known as colostrums which is usually sticky and yellow contains more proteins and anti bodies the milk does not contain iron.

The iron needed for the formation of the heamoglobin of the RBC is stored in the liver of the foetus during gestation.

The baby should be breast fed as long as it is possible at least for 6 months before weaning.

Advantages of breast feeding

· It is safe no chance of infection

· It creates a special bond between mother and child i.e. Love and security

· It has a suitable ph

· It contains nutrients in the right portions

· It does not require preparations

Reasons for substitution of mothers milk

1. Diseases i.e.Breast cancer, HIV/ AIDS, TB etc

2. Lack of lactation

3. Multiple babies

4. Mothers’ death

5. Working mother

Common problems in infancy (child hood)

1. Constipation

2. Excessive crying

3. Heat rash

4. Nappy rashes

5. Diarrhoea

6. Colic [pain abdomen]

Stages of growth in infancy

1. 0-3 months old

The baby can lay on its back can try to roll over. It can make movements with fingers and can make slight noises

2. 24-5 months old

· The baby can seat up with support and keep his head upright

· The baby can coordinate eye and hand movement

· The baby can recognize its parents

3. 6-7 months old

The baby now does not need support to stand and start locomotion through crowing.

4. 8-9 months

The baby stands with support. It can hold objects but cannot throw.

5. 10-12 months old

The baby can stand on its own with out support but cannot walk. It can walk with support. It can utter afew repeated words.

6. 13-18months old

At this time the baby becomes very independent. He can walk and run without help. It can feed its self. It can turn objects up and down. It can express emotions and can get annoyed. The baby should have 12-16 teeth.2-3 years old

The child is now confident and plays with toys. The child is social and improves motor co-ordination

7. 3-6 years old

This is a very crucial stage of life. This is because the child is taken to school and learning, is usually by imitation. The school environment should be rich to orient the child to quick learning. The child should get maximum exposure of the environment.

8. 7-12years old

This is the age of primary school where the child learns many things including how to get along with other children and adults. This is the time period when the child can understand social and political issues of the country

2. ADOLESCENCE

Adolescence is the period between child hood and adult hood. It occurs at the age of 11-13 in girls and 12-14 in boys. This is a period accompanied by physical and emotional change that occurs in both boys and girls to prepare their bodies for parenthood the changes are controlled by sex hormones which develop secondary sexual characteristics. This period is also known as puberty

Changes in boys at puberty

· Voice becomes deepened

· Chest widens

· Growth of hair and beard in pubic regions

· Wet dreams begin

Changes in girls at puberty

· Hair grows in the pubic regions

· Voice becomes sharp

· Breasts enlarge and hips broden

· Pelvic gridle widens

· Menstruation starts

· Uterus enlarges

Common changes in both girls and boys

· Sweating increases

· Attraction of the opposite sex

· Body increase in size due to rapid growth

· Enlargement of sex organs

· Hair grows in pubic regions and under arms

· Secretion of sex hormones

Personal hygiene during adolescence

1. Take a bath twice a day

2. At this time the body produces more sweat, use good quality soap

3. Wear clean clothes all the time

4. Wash soiled bedding and clothes as often as possible

5. Girls should wear good tampons or sanitary towels during menstruation and change them often. Wash your hands with soap and clean water after handling soiled tampons or pads

Male circumcision

The term circumcision has a Latin origin which means to cut around. Male circumcision is done for religious reasons as well as health reasons because it reduces the risk of penis cancer

Female circumscion or female genital mutilation

This practice is based on traditional beliefs which is seen as maintaining virginity improving fertility and discouraging prostitution . However it does not have a scientific logical or religion basis. It is taken as a form of child abuse. It causes physiological trauma, infections and pain.

SEX EDUCATION

Children should be taught sex education from when they are young. This enables them to understand the developmental stage of puberty and adolescence.

The knowledge of sex and correct attitude towards the sexual life are important for a happy life. Sex education are provided at school home and place of worship.

3. ADULT HOOD

Adults are physiological and physically mature to make families. The male becomes the husband and the head of the family. The husband has to respect his wife and the children. He should provide basic needs such as

· Food

· Shelter

· Education

· Clothes etc

The wife and husband should work together to ensure harmony in the family as it depends on the relationship between the two partners each should understand and tolerate the other, they should discuss family matters the two should bring up the children molary upright. They should provide for protection and counsel and love their children. The children should help the parents in house hold.

In the family boys and girls should be given equally, equal right without any discrimination.

GENDER ROLES

Role of male in the society

1. He should provide basic needs.

2. To provide security

3. To provide financial support

4. To engage in economic activities in the society

5. Should be disciplined and respect other members of the society

6. Plan for the future support of the family

Roles of female in the society

1. To bring up the children moraly upright.

2. To maintain house hold

3. To provide love and support to the family

4. To practice in decision making

5. To accept male as head of the family

6. They should maintain the same culture

7. To give birth

DIVISION OF LABOUR

Division of labour refers to allocation of the responsibities within a family or community example women perform the primary roles of reproduction child rearing and home management. On other hand she plays a major role in development of national economy, man has to provide basic needs of the families and he has to support the wife to maintain the harmony of the family.

Gender imbalance

Women are usually over worked due to uneven division of labour. It unfortunate women are the principle producer even though men control the family and enjoy all the benefits. The gender imbalances make the role of women in development difficult.

Solution to the problem

1. Education equally

2. Enforcement of laws

3. Counseling for the family stability

4. Empowerment of female

5. Fight against lack of education and awareness

6. Fight against poverty

7. Proper family planning

8. Fight against the ignorance of female

Separation

This is the stage where by the husband and the wife agree or are allowed by the court to leave a part due to strained relationships during separation. The two are supposed to think and re consider their decision even if he is not living with them.

Divorce

Divorce (or the dissolution of marriage) is the termination of a marital union, the canceling or reorganizing of the legal duties and responsibilities of marriage, thus dissolving the bonds of matrimony between a married couple under the rule of law of the particular country and/or state

Divide property however it is not good for child proper growth. It will lead to misery and psychological instability.

Adoption

A couple does not get children due to sterility or other biological reasons may adopt a child. The adopted child should be entitled to the same rights and benefits as should a child born by that parent

4. OLD AGE

This is the age of senescence which begins at the age of 45 -55 or soon after menopause in women

Mental and physical change during this age

1. Grey hair due to lack of melanin

2. Wrinkle skin due to the accumulation of dead cells

3. Hearing defects

4. Eye sight defects

5. Loss of memory

6. Lack of patience

7. Breathing problems

8. General weakness

9. Loss of appetite and digestion problems

10. Hormonal disorders i.e. diabetes

11. Weak muscle tone (elasticity)

12. Tooth decay

13. They become more susceptible

14. Ostropus

15. Decreased blood circulation and weak heart muscle

16. Delay in hearing

17. Lack of concentration

18. Pregnant women are not allowed to eat eggs

5. Ageing

It refers to the physical deterioration of an individual as the age increases the age increase the study of ageing is called gerontology. The progressive decline of biological function with age is called senility.

Longedity (life span)

This is the period one lives from birth to death. People age at different rates. Ageing rate is determined by the genetical and the environmental factors

Factors that affect physical deteriation in humans

· Environmental factors

1. Amount of food

2. Type of food

3. Diseases and infections

4. Poverty

5. Emotional disturbances

6. Alcoholism and drug abuse

7. Chemicals due to pollution

8. Weather and climate

· Genetical factors

1. A small number of individuals carry a defective gene that causes Werner syndrome which causes pre mature ageing

6. Death

This is the end of life the cells and all the body processes stop to function and the reaction reduces

Social cultural factors that affect growth and development

1. Traditional believe

Pregnant women are not allowed to eat egg

2. Poverty

Some families cannot afford to buy food containing important nutrients for growth i.e. Medical expenses

3. Religion

FGM which cause trauma distress frustration infection and psychological effects hence affects growth.

Some people are not allowed to go to the hospitals and they fail to get medical treatment.

4. Ignorance

· Lack of knowledge of proper diet

· Lack of awareness of proper diet

· Lack of education

· Lack of media publicity

· Lack of sex education

GROWTH AND DEVELOPMENT IN FLOWERING PLANTS

Development are changes that occur in an organism from the time of fertilization to the formation of an adult body.

In flowering plants, development starts with the growth of zygote into an embryo.

In most flowering plants growth starts when the seed begin to germinate.

Germination is the process by which the seed develops into seedling (young plants)

A summary of changes which occur during seed germing

· The seed absorbs water through micropyle and enlarge.

· Later on the testa bursts and the radide emerges. Rsdicle continues to elongate and gives rise to many roots.

· Then the plumule emerges.at this stage the young plant is called a seedling.

CONDITION NECESSARY FOR GERMINATION

1. WATER

· It is a suitable medium of enzymes to break down the stored food into suitable form.

· It hydrolize food substance into glucose

· It is used to transport food materials between the cell/ to where they are used as source of energy.

· It softens the seed coat/testa so that it ruptures (bursts easily)

2. OXYGEN/ AIR:

In the dormant condition the seeds respiratory rate is very low and so oxygen is required in very small quantities. But for germination, oxygen is needed in large quantities. The seeds obtain oxygen that is dissolved in water and from the air contained in the soil. If soil conditions are too wet, an anaerobic condition persists, and seeds may not be able to germinate

3. Temperature:

Germination can take place over a wide range of temperature and is specific to individual crop types, and can be specific to varieties. The optimum for most crops is between 65-75°F, but exceptions do apply. For example lettuce germinates best at 65°F and can be inhibited at temperatures over 68°F while peppers and eggplants prefer warmer temperatures around 80°F and will not germinate well at cooler temperatures. If your soil is too cold or too hot, your seeds may not sprout. Check your seed packet to find the best temperature needed for your seeds.

4. Light:

Light has varied effects on germinating seeds of different plants. Some seeds need light for germination, while in some seeds germination is hindered by light. Most wild species of flowers and herbs prefer darkness for germination and should be planted deep in the soil while most modern vegetable crops prefer light or are not affected by it, and are planted shallowly to allow small amounts of light to filter through the soil.

TYPES OF GERMINATION

1. EPIGEAL GERMINATION

· In epigeal germination the hypoctyl elongates first, plumule and cotyledons are brought above the soil surface.

· Seeds showing epigeal germination generally have small cotyledons, which once exposed to light develops chrolophyll and start to photosythesis e.g beans and sunflower.

epigeal germination diagram

1. HYPOGEAL GERMINATION

In hypogeal germination the epicotyl elongates first and plumule is pushed upwards out of the ground.

· These seeds have large food reserved in their cotyledons

· Example of the seeds are maize and wheat

hypogeal germination diagram

NOTE:

Germination occurs only in a seed which is viable (whose embry is alive)

MARISTEMS

· Maristerms are regions in plants where growth and development takes place.

· Main maristems are located at the tip of shoot and at the tip of roots.

· Active cell division and cell elongation takes place in maristems.

· The growing region of the radicle and hence the root has three main regions, including regions of cell division, elongation and differentation.

Types of Maristems

1. Apical maristems

2. Lateral maristems

· Apical maristems bring about an increase in length and height of roots and shoots.

· Lateral maristems give rise to branches of shoot. Lateral maristems bring about the increase in growth of the shoots and roots.

SEED DORMANCY

Seed dormancy is an inhibition of growth of an organism or part of it.

Some viable seeds will not germinate even when supplied with proper amounts of heat, water and oxygen. This is the period of reduce activity during which growth does not occur.

Factors which bring about seed dormany

· Nature of the testa

· Presence of certain chemicals

· After ripening

· Food and water

· Climate

· Emboryo may not be full develope

· Lack of moisture and oxygen

1. NATURE OF THE TESTA

Some seeds the testa may be impermeable to oxygen and water. In such seeds time is required before the testa becomes permeable. The testa may also be hard – preventing the radicle and plumule form emerging.

2, Presence of certain chemicals

Certain chemicals present in either the seed or fruit are known to pevent seed germination. These chemicals are removed by leaching.

3. AFTER – RIPENING

Some seeds will not germinate immediately after harvest. It has been found out that at that time embroys are not fully developed. Such seeds have to go to be stored for some time so that the embryo develop fully. The period is called after-opening.

WAYS OF BREAKING SEED DORMANCY

· Provide water

· Provide air

· Provide suitable temperature

· Ensure seed embryo is mature

IMPORTANCE OF SEED DORMANCY.

• Seed domacy has a survival value to plants seeds can survive for a long period especially in adverse envirinmental conditions such as drought, extreme temperature and shortage of food.

• If all seeds germinate at the same time in such conditions all seedling would perish.

• Seed dormancy helps an organism to with stand unfavourable conditions such as cold and drought shortage of water etc

It allows time for dispersal of seeds by agents such as water and wind

Seed viability

The seed which retains its capability to germinate are known as viable and the ability is known as viability

FACTORS AFFECT THE VIABILIRY OF SEEDS

1. Seed maturity

2. Environmental condition

3. Nature of a testa

4. Availability of moisture

5. Temperature

6. Light intensity

7. Storage condition.

Growth regions of a seedling

The growth of the radical and the plumule causes the elongation of the seedling. The rate of the growth can be measured at the tip of the root and shoot cells at the root and shoot tips have high capacity to divide.

The dividing cells are known as meristematic cells, these cells make a tissue known as apical meristem. These cells rapidly undergo mitosis to provide growth which increases in size of the shoot and root.

Growth in the tip of the root and shoot is known as primary growth.

Widening of the plant to form the trunk and hard wood is called secondary growth.

Difference between growth in animals and plants

Animals

Plants

Growth takes place through the body

It is restricted t o certain regions

Broken parts such as limbs cannot re generate

Broken parts such as branches can re generate or replace

Growth involves cell division but not increase in cell size

Growth involves in cell division rapid cell elongation and cell differentiation

Growth is not limited by temperature

It is influenced by environmental factors such as temperature

Growth leads to definite shape

Growth leads to indefinite shape or branched shape

GENETICS

Genetics is a branch of science which deals with the study of inheritance and variation.

Definition of terms

1. Heredity

Is a passing of features from parents to their young.

2. Variation

Possessing of characteristics which are different from these of the parents and other offsprings.

3. Genotype

Is the genetic constitution or make up of an organism

4. Phenotype

Is the outward or physical appearance of an organism

5. Dominant gene

Is a gene that prevents the expression of another gene.

6. Recessive gene

Is a gene that is masked by another gene.

7. Hamozygous

Is a condition where by the two genes for a given trait are similar/ alike

8. Heterozypous

Is a condition where the two genes for a trait are different.

9. Gene

Is a part of chromosome that carries the genetic material called DNA. Are also refered to as nucleotide chemical units of inheritance arranged along the chromosomes. They are called hereditary factors.

10. Trait

Are characteristics inherited by individual from their parents

11. Allele

Is an altenative form of a gene controlling the same characteristics but produce different effect

Example: T-tallness and t- shortness

12. MONOHYBRID CROSS

Are offspring produced by crssin two individual with different character

e.g. homozygou green poded plant (GG) andhomozygous yellow poded plant (gg)

13. FIRST FILLIAL GENERATION (F₁)

Is the first generation of offsprings produced after crosing the parental genotypes.

14. SECOND FILLIAL GENERATION (F₂)

Are offsprings produced by selfing the F₁ generation

15. MONOHYBRID INHERITACE

This is unheritance of one pair of constrasting (different characteristics e.g height where an individual is either tall or short.

16. DYHIBRID INHERITANCE

This is inheritance of two pairs of characteristics

Example: - pure tall pea plant with colours flowers and dwaf pea plant prossesin g white flowers.

17. EPITASIS

It is the interaction between the two different known as allelic dominant genes

18. Pedigree

Is the historical or ancestral record of individuals shown in a chart ,table or diagram

19. CHROMOSOMES

They are thread like structures found in the nucleus of the cell they are only visible when a cell nucleus is about to divide. Every nucleus of the cell of the same species has a constant number of chromosomes e.g.

Drosophila has 8 chromosomes, fruit fly pea plant has 40chromosomes sheep has 56 wheat has 14 chromosomes maize has 20 chromosomes.

Each member of the chromosome pair is known as homologous chromosome

Types of chromosomes

There are two types of chromosomes in the human body

1. Autosomes

2. Heterosomes

Autosomes

These are also known as autosomal chromosomes. They carry all genetic information except that of sex. In humans autosomes are 44 in numbers forming 22pairs

Heterosomes

These are also known as sex chromosomes these chromosomes determine the sex of the organism in humans. One pair is responsible for the determination of sex

Diploid and haploid nuclei

Diploid nucleus has the chromosomes occurring as homologous pair e.g 23 pairs in the human this is denas 2n diploid nuclei are found in the gamets

Haploid nuclei have only one set of unpaired chromosomes. In 23 chromosomes are there haploid nuclei are denoted as n diploid cells are formed after fertilization

GENETIC MATERIALS

Genes are nucleotide chemical units of inheritance arranged along the chromosome and are capable of being replicated and mutated.

Each gene occupies a specific location on a chromosome this location is known as locus (plural is loci) each chromosome contains many genes.

Homologous chromosomes when paired together will have similar or different genes called alleles.

An alleles is an alternative form of gene controlling the same character out producing different effects. The gene can control color of the skin

NUCLEIC ACID

Nucleic acids are polymeric macromolecules, or large biological molecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides. Each nucleotide has three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is deoxyribose, the polymer is DNA. If the sugar is ribose, the polymer is RNA.

Together with proteins, nucleic acids are the most important biological macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information—in other words, information is conveyed through the nucleic acid sequence, or the order of nucleotides within a DNA or RNA molecule. Strings of nucleotides strung together in a specific sequence are the mechanism for storing and transmitting hereditary, or genetic, information via protein synthesis.

DNA (deoxyribo nucleic acid)

DNA has a double stranded shape or coil twisted like a ladder to form a double helix.

DNA is the genetic material contained in the genes

COMPONENTS OF DNA

· Deoxyribase sugar

· Phasphate group

· Organic base or nitrogen bases

Nitrogenouse base

· Adenine (A)

· Guanine (G)

· Uracid (U)

· Cytosine (C)

· Guanine (T)

Functions of DNA

1. There are genetic material which are responsible for genetic characteristics

2. They assemble the amino acids to form a protein molecule

RNA (ribonucleic acid)

The RNA molecule is responsible for carrying genetic information from the DNA molecule to the ribosome which is the sight of the protein synthesis

TYPES OF RNA

Messenger RNA – carries information from the nucleus in from of base triplets.

Transfer RNA – It transfers the apropriate amino acids to the ribosome.

DIFFERENCE BETWEEN DNA & RNA

DNA	RNA
Has a deoxyribase sugar	Has a ribase sugar
Has a double stand	has a single stand
Found in the nucleous, mitochondria and chroloplast	Found in nucleus and cyto plasm.
Has organic bases, sytosine, guanine adenine and thymine	Has organic bases, sytosine guanine, adenine and uracid

LAWS OF INHERITANCE : MENDEL’S PRINCIPLES

Historical background of genetics

Father of genetics is Gregory Mendel

Mendel’s experiment

Mendel has selected garden pea plants [pisum sativa]

Reasons for selecting pisum sativa

1. The garden pea has many contrasting and easily recognized characteristics.

2. The hybrid obtained from the cross fertilization was fertile

3. The flowers of a garden pea are bi sexual and naturally self pollinated

4. The garden pea plant matures relatively fast producing many off springs (seeds)

1. LAW OF SEGREGATION

It states that “characteristics of an organism are controlled by internal factors (genes)occuring in a pair is carried in each gamete”

2. LAW OF INDEPENDENT ASSORTMENT

“ Each of the 2 allels of one gene may combine randomly with either of the alleles of another gene independently”

PUNNET SQUARE

· Is a chart showing the possible combination of factors among the offspring of a cross.

· It is used to show the formation of zygotes.

Female gametes are placed on the right while male gamets are placed on the left side.

â™‚ Male

+ Female

Example:

A cross between homozygous tall (TT) and homozygaus dwarf (tt) plant can be illustrated as follows:

Let assume tall is male and dwarf is female

Test cross

A cross used to cross an individual of unknown genotype with a homozygous recessive individual

Example:- A homozygous dominant individual (Tt) will phenotypically appear the same.

BACK CROSS

In the crossing of individual of unknown genotype with the homozygous parent.

This is another form of test cross, but the difference is that in test cross, it is crossed with any individual while in back cross with a parente.g: if the individual is homozygous (bb)

DIHYBRID INHERITANCE

This is the inheritance of two pair of characteristics

e.g: TTRR – Tall and coloured

ttrr – dwarf and white

TT RR

TT Rr

Tt Rr

TTRr

TTrr

Tt Rr

Tt rr

Tt RR

Tt Rr

tt RR

tt Rr

Tt Rr

Tt rr

tt Rr

ttrr

Phenotypic ratio

Tall and coloured 9

Tall and white 3

Dwarf and coloured 3

Drawf and white 1

Example:

Mendel crossed a plant from a pure line producing round- yellow seeds with a plant from a line of wrinkled-green seeds. The seeds produces representing F1 were all round and yellow.

Show the results of cross between the two

Solution: -

Let: - Round-yellow seeds be dominant RY

Wrinkled –green seed be receive ry

TRY

RRYY

RRYy

Ry YY

RrYy

RRYy

Rryy

RrYy

Rryy

RrYy

rryy

rrYy

RrYy

Rryy

rrYy

rryy

Phenotypic ratio

Round and yellow 9

Round and green 3

Wrinkled and yellow 3

Wrinkled and green 1

DOMINANCE

Dominance is a state of one character /gene from ane parent masking the corresponding character from another parent.

Types of dominance

1. Complete dominance

2. Incomplete dominance

3. Co-dominance

1. COMPLETE DOMINANCE

· Is the dominance where by one gene masks the expression of the other gene.

· A dominant gene always masks a recessive gene when the two occur together.

EXAMPLE:

1. A man homozygote for brown iris marries a women who has blue iris. Show the results of F₁. What colour would the iris of the cross between 2 members of F₁?

Solution: -

The gene for brown iris is completely dominant over gene for blow iris in woman.

Let gene for brown be B and b for black

Genotypes - all are Bb

Selfing F₁

Genotypes - BB,Bh,bb

Phenotypes - 3 Brown iris, 1 brown iris

Genotypic ration - 1 : 2 : 1

BB Bb bb

2. A pure purple flowered pea plant was crossed with pure white pea plant. Offsprings for F1 were phenotypically all purple flowered plants when F₁ was selved a mixture of puple pea flowered and white pea plant were produced at an approximate ratio of 3:1

Solution: -

Let gene for purple be P and white be p

Genotypes : all are Pp

Phenotypes : all have purple flower

Self F₁

Genotype - PP, Pp, pp

Phenotypic ratio - 3 : 1

Genotypic ratio - 1 : 2 : 1

2. INCOMPLETE DOMINANCE

In incomplete dominance there is no dominant or recessive gene, but both express themselves equally. It results in a heterozygous individual wich does not resemble any of the heterozygous individual which does not resemble any of the parents.

Example: -

1. A red flowered rose was crossed with white rose and all members of F1 were pink. When pink were selfed, a mixture of red, pink and white flowered plants were obtained.

Solution:-

R – Red , G – White

Genotypes : all are RG

Phenotype : all are pink

Genotypes - RR, RG, GG

Genotypic ratio - RR : RG : GG

1 : 2 : 1

Phenotypic ratio - 1 red : 2 pink : 1green

3. CO-DOMINANCE

In co- dominance genes from both parents are dominant and are phenotypically expressed in the offspring.

Example: A red cow is mated whith white bull. In F1 generation all of offsprings have equal patches of red and white fur. Therefore neither red or white gene is dominant over the other such cattle and called Roan.

When a roan cow is mated with roan bull, offsprings may be red, roan or white wated in the ratio of 1 : 2 : 1

W - white ful

Let R – Red

Genotypes – all are RW

Phenotype – all are Roa

Phenotypes ratio - 1 Red : 2 Roan : 1 White

Genotypic ratio - RR : RW : WW

1 : 2 : 1

GENETICS 2

SIMPLE MENDELIAN TRAINTS

The following are example of mendelion’s traints in man

1. ALBINISM

Albinism is absence of pigmentation melanin in human skin/ animals or plants. This pigmentation is responsible for dark colour of the skin. As a result the person has white hair, pink eyes and light skin. In plant are characterized by lack of chlorophyll

It is controlled by a recessive gene. Human showing this disor der must be homozygous recessive. Heterozygous are normal but carreer.

Examples

1. What will be the result of normal man who married an albino woman?

Solution: -

Let gene fornormal be A and Albino be a

Phenotype - all are normal (Heterozygour)

2. What would be the result of a cross between heterozygous parents?

Genotype – AA, Aa and aa

Phenotype – normal man, carrier and albino

3. What would be the result of crossed between heterozygous parent with an albino parent.

      Solution: -

             Gene : Aa        -           heterozygous parent
                        aa        -           albino parent

Genotypes - Aa and aa

Phenotypes - half normal/ carries and albinos.

4. What would be the result of crossed between heterozygous parent and homozygous nomal parent

         Solution:-
         Heterozygous Aa, homozygous AA

Genotypes - AA, Aa

Phenotypes - all are normal (normal, carriers)

2. ACHONDROPLASIA

Achondoplasia is a disorder that is characterized by a shorted body, legs and hands. It is controlled by a dominant gene. Individuals with this disoders are Homozygous dominant or Heterozygous. Homozygous recessive are perfectlly normal

Examples: -

1. What would be the result of a normal man who married an achondroplasia woman.

Solution: -

Genes for normal man - aa

Genes for achondroplasia women - AA

Phenotypes - All are anchondroplasia

Genotypes - Aa

2. What would be the result of a cross between an achondroplasia woman who is homozygous and achondroplasia man who is heterozygous?

Solution: -

- AA, Aa

Phenotypes - All achondroplasia

3. What would be the result of a cross between heterozygous parents?

Solution: -

Phenotypes - 3 Achondroplasia, 1 Normal

Genotypes - AA, Aa, aa

Phenotypic ratio - 3: 1

Genotypic ratio - 1 : 2 : 1

3. HAEMOPHILIA

Haemophilia is a hereditary trait characterized by delayed blood clotting. The result is prolonged bleeding even small injuries can lead to death. The haemophilic girl rarely live beyond puberty because of excessive menstrual bleeding. It causes high mortality rate.

It is controlled by recessive gene. Heterozygous are normal/carries but homozygous individuals are haemophilic.

Worked example: -

If a norman man married a haemophilic woman, the offsprings would be

Solution: -

Let genotype for the man X ^HY and woman X ^hY ^h

· A haemophilic man will be X ^hy

· Haemopholic female will be X ^h X ^h

· H – not suffering from haemopholic while h – haemopholic

4. COLOUR BLINDNESS

Is the hereditary trait characterized by inability to detect certain colours of the spectrum. The common colour blindness is inability to distinguish between red from green.

It is controlled by a recessive gene. Homozygous individual are colour blind while heterozygous are nomal or carrier.

e.g . If a colour blindness man marries a nomal woman, the offspring will be as follows.

Let B – normal

b - Colour blind

1. SICKLE CELL DISEASE

This is a genetic disorder which makes the red blood cell acqure sickle shape under certain conditions. It may occur when the person is attacked by certain deseases. e.g.malaria. Also when oxygen tension in the atmosphere is very low. The sickled cells ability to carry oxygen is reduced

It is controlled by a Recessive gene. Homozygous individuals are sickled cell while heterozygous individuals are normal/ carriers.

NOTE:

HbA –

HbS

* If a carrier man marries a carrier woman the offsprings will be

- perfect normalv

- sickle cell trail

- sickle cell anaemia

6. TONGUE ROLLING

This is a heriditary trail which is charactrerized by rolling a tongue into a U – shape. It is controlled by a dominant gene. Heterozygous and homozygous individuals are tongue rollers. Recessive are not tongue rollers.

TRAITS/ DISORDERS AND THEIR CONTROLLED GENE

DOMINANT GENE

RECESSIVE GENE

Achondroplasia

Haemosphilia

Tongue rolling

Colour blind

Night blindness

Sickle cell

Brown iris

Blue iris

Having more than 5 fingers & toes

Normal night vision

Albinism

Normal number of finger and toes.

HOW TO SOLVE GENETIC PROBLEMS BY USING PUNNET SQUARE

1. In human beings normal skin pigment (melanin) is dominant over albinism. An albino male mates with a heterozygous female. If the female gives birth to 6 fraternal twins what will be the propaple genotypic and phenotypic ratio of the offspring?

Solution: -

i) Let letter A - dominant gene

a - recessive gene (albinism)

• Write the genotypes of the parents

(male) aa x Aa (female)

ii) Use these genotype to complete the punnet square

iii)Summarize the genotypic and phenotypic ratios

Genotypic ration - Aa : aa = 1Aa: 1aa

Phenotypic ration - ½ normal skin pigmented : albino = 1:1

2. In human beings normal skin pigment is dominant (A) over albinism (a) one couple with nomal pigment mate and produce six fraternal twix. Out of 6, 4 have normal skin pigment and 2 are albino. What are the genotypes of the parents?

Solution: -

1. Write complete/partial parents genotypes and offspring

Parents A

Four nomal skin offspring A

Since normal skin is dominant, each of parent and 4 children must have at least one dominant gene

2. Since albino gene is recessive, 2 albino offspring are homozygous recessive (aa)

Two albino offsprings (aa)

A - (Normal skin parent)x A - (normal skinparent)

A - (4 normal offspring aa - (2 albino offspring)

Since one gene for albino comes from each parent. Therefore each parent is heterozygous (Aa)

RHESUS FACTOR

About 85% of the human population has a gene located on the chromosomes number one that produces a function protein called ANTIGEN & (Rhesus factor)

Individuals with rhesus factor are rhesus positive (Rh⁺) and the remain 15% do not have this factor are rhesus negative (Rh^-). Rh⁺ is dominant over Rh^-.

Rhesus antibody is normally absent in plasma of human blood. The Rh^- people produce this antbody if Rh⁺ blood is transfused to them. These Rh+ antigens react with rhesus antibody causing agglutination. The present or absena of Rh factor gives the blood groups the + or – signs.

The table below shows the reactions of blood types with and without Rh factor.

KEY: (√) - No agglutination

(x) - Agglutination

WORKED EXAMPLE

A Rh⁺ man marries a woman who is Rh^- and produces 10 children, what will be the phenotypes of the children

SEX INHERITANCE

Sex is a phenotypic character, it is dependent upon the genotype and enviroment. In sexually reproducing organisms, each individual is a product of a male and a female. Each individual receives an equal number of chromosome from male and female body. Fo example each individual receives 23 chromosomes from the mother and 23 from the father.

· In many species female chromosomes (sex) are XX and male are XY

The chromosomal mechanism of sex determonation varies in different organisms

Example: -

Organisms

Gametes

Zygotes

Ova

Sperm

Female

Males

Drosophila, Human beings, Grasshoppers, Birds, Moths, Butterflies

SEX DIFERENTATION IN HUMAN BEINGS

Sex as a distinct character becomes a reality only after a long and complex period of development. In mamals the early embryo has no male or female gonad. Hence it is “Neutral” and remains that way even after early development of gonads.

• The embryonic gonads which develope consist of 2 parts

1. Cortex - an external layer developing to ovary

2. Medulla - an internal layer develoing to testes

• In addition there are 2 ducts in the neutra embryo

1. Mullerian duct which persist if indivudual becomes a male.

2. Wolfian duct persist if the individual becomes a male

After the neutral stage, specific sex determiners take over and stimulate the development of sex organ that are either male or female.

If the embryo’s chromosomes is XY the medula part enlarges and begins to differentiate while cortex portion disappears.

If the embryo is XX the cortical/ cortex portion develops while the medullary part disappears.

SEX LINKAGE

Sex linked genes carried on sex chromosomes but have nothing to do with sex. Traits whose expression is governed by sex linked traits are called sex linked traits .

One kind of colour blindness is an example of sex linked trait in human beings located on the X – chromosome. Example of other linked are haemophilia (bleeder’s diseases).

VARIATION

Variation is the possession of characteristics which are different from the parent and other offsprings.

Types of variation.

1. Continuous variation

Is the variation which show intermediate form between any two extremes i.e there is no clear cut distinction between two extremes.

Example in group length ranges from shortest to tallest with several intermediaries continuos variation arises from interaction between genes and environment.

2. Discontinuos variation

Is the variation which show clear cut distinction from one form to another form.

Example: -

In human population an individual is either a male or a female, ability to roll the tongue, albinism, blood group (A,AB,O) and rhesus factor.

Environment does not influence the characteristics that show discontinuor variation.

Example blood group can not be altered by environment.

Cause of variation

1. Environment Factors

Food – lack of food of a certain diet leads to deficiency diseases such as Kwashiokor. Lack of enough food causes starvation. Also pathogens causes diseases in organism making the individual different from the normal ones.

2. Genetic factors

(a)Meiosis – during meiosis there is segregation of different gametes.

· This reduces the chance of pairs of chromosomes producing a wide variety of different gametes. This reduces the chance of individuals being the same.

(b) Fertilization – during fertilization the nuclei of male and female gametes fuse.

· This permits parental genes to be brought together in different combinations.

· This may lead to desirable and undesirable qualities of parents be combined in the offspring.

(c) Mutation- This is a sudden change in gene which can be inherited are caused by mutagens as x rays, cosmic rays, chemicals as mustard gas. The individual is called a mutant after undergoing mutation and appears different from the rest of the population.

3. Migration

As species are not normally informaly distributed but occurs in small isolated population called demes. If members from the deme migrate and mate with members of another deme the offspring that results have characteristics that are different from those of both parents.

TYPES OF CHARACTERS

1. Acquired characters

These are traits an individual develops as a result of adaptation to the environment. Example: - Walking style. They are never inherited and are also know as no-heritable characteristics

2. Inherited characters

Are traits passed on from parents to the offsprings through sexual reproduction.Are also called heritable characteristics.

Difference between acquired and heritable

ACQUIRED CHARACTERISTICS

HERITABLE CHARACTERISTICS

1.Are due to the environment

2.Can not reappear in offspring.

3.Sometimes are changable in life time (one way lose weight)

1.Are due to genes

2.Re-appear in offsprings

3.Mainly unchangable in life time (height

MUTATION

Mutation are changes in the genetic material in the gametes.

• It includes appearance of new characters that have never been before in that population

• Individuals who undergone mutation are called Mutants

•Mutation can be due to

1. Change in a gene itself

2. Change in arrangement of genes

3. Loss of chromosomes (due to unbalanced meiosis)

• Mutation can be caused by agents known as Mutagens

§ X-rays

§ Cosmic rays

§ Heavy metal (lead & mercury)

TYPES OF MUTATION

1. Gene mutation

2. Chromosomal mutation

1. GENE MUTATION

Gene mutation occurr as a result of altering the chemical structure of genes

• There is a change in the sequence of nucleotides is the segments of DNA coresponding to one gene. This inturn alters the sequence of amino acids required in synthesis of a particular protein.

• The protein formed will be different from the normal ones and produce a profound effects on both the structure and development of an organism Example: sickle cell, dwarfism.

TYPES OF GENE MUTATION

1. Substitution

2. Insertion

3. Deletion

4. Inversion

i. SUBSTITUTION

This is the replecement of one or more portions of a gene with a new one. E.g. A thymine (T) on ATA on the DNA molecule is replaced by cytocise (C) and result to ACA on the DNA

This is examplified in sickle cell anaemia only one nucleotide is changed. This kind of mutation involving the change of one nucleotide is called Point Mutation.

ii. INSERTION

This involves adding a new portion of a gene to an existing one. Example: If the base Guanine (G) is inserted between two Adenine result into AGA which does not code for any amino acid.

iii. DELETION

Deletion is the remove of a portion of a gene Example: -If base Guanine (G) is deleted in a base triplet CGC resulting into alteration of base sequence reducing the number of amino acids.

iv. INVERSION

A portion of DNA strand cuts and rotates through 180° the invesion results in alteration of the base sequence at this part.

Example: -A base triplet CTA can have its base thymine (T) and Adenine (A) cut and rotated. The result is CAT which is different from amino acid.

2.. CHROMOSOMES MUTATION

Chromosomes mutation involves changes in the structure of the chromosomes. During meiosis homologous chromosomes interwine at several points called chiasmata and create opportunity for various changes on the chromatids leading to mutation.

TYPES OF CHROMOSOME MUTATION

1. Deletion

2. Duplication

3. Inversion

4. Translocation

5. Non-disjunction

6. Polypoidy

1. DELETION : This occurs when a portion of the chromosome breaks off and fails to reconnect to any of the chromatids, The result is the loss of genetic materials.

Deletion can be caused by error in chromosomal crossover durin meiosis. These causes serious genetic deseases

       2. DUPLICATION
             This occurs when a portion of the chromosome replicates itself adding extra length. The result is addition of a set of genes which is a duplication

This may result to over emphasizing of a trait in an organism.

    3. INVERSION
        This occurs when a middle piece of the chromosomes breack and rotates at 180° and rejoins the chromatid. This has the effect of reversing the gene sequence.

4. TRANSLOCATION

This occur when a portion of one chromosome breaks off and becomes attached to another chromatid of non-homologous pair. The result is transfer of genes from one pair of homologous chromosome to another.

5. NON-DISJUNCTION

This kind of chromosomal mutation is caused by addition or loss of one or more chromosomes. This occurs during meiosis where homologous chromosomes fail to separate. This results in some gametes having more chromosomes that others.

Example of non – disjunction

(a) DOWN’S SYNDROME

This is caused by presence of an extra chromosome number 21 individuals with this defect have a total of 47 chromosomes they have

· Resistance to infection

· Mentally retarded

· Have thick tongue

· Short body

Also children of old parents (above 40 years woman and 55 man) have increased chance of Down’s syndrome.

(b) KLINEFELTER’S SYNDROME

This is caused by failure of X chromosome to separate during the process of egg formation. An individual with this condition has two X chromosome and one Y chromosome (XXY). They are – outwardly male but may also have female characteristics.

This is an individual with 45 (44 + x 0) chromosome in a cell instead of 46 (44 +xx). Individual with this condition have one X and no Y i.e (XO) they individual is sterile and abnormally short female.

6. POLYPLOIDY

Occurs if the whole set of chromomes doubles after fertilization, where the spindle fail to be formed and the cell does not divide.It is rare in animals but common in plants

7. SICKLE CELL ANAEMIA

Sickle cell anaemia is an example of gene mutation. The normal haemoglobin is entirely replaced by an abnormal haemoglobin known as haemoglobin S

In sickle cell anaemia, the glutamic acid is replaced by another amino acid, the valine forming a haemoglobin s denoted by Hbs. Normal haemoglobin is denoted by HbA.

Haemoglobin S begins to crystallize when Oxygen concentration falls and causes red blood cell to assume the shape sickle. Half the number of red blood cell is sickle

GENETIC COUNSELLING

Genetic information is used to advice couples who have hereditary disorders about chances of children inheriting the disorders. Genetic information could also be used in choosing marriage partners.

GENETIC ENGINEERING

This is the alteration of the structure of DNA by man.

• Genetic engineering enables man to carry out reseach.

§ Manufacture protein (insulin)

§ Improve animal and plant breeds

§ Correct genetic disorders

· Genetic engineering is the technique of changing the genotypes of an organism. It involves inserting genes from one organism into the chromosomes of another organisms. Once inserted the foreign genes work as if they were in the organism they were taken from.

APPLICATION OF GENETICS

1. MEDICINE

Genetis engineering has enabled biologists to program and make useful substance. For example the gene in man that produces insulin was inserted into escherichia colia for producing pure insulin in large quantities.

• Human growth hormone ha also been made by using bacteria which the proper gene has been added.

• Also blood cloting factors such as fibrinogen needed by haemophiliacs are produce.

· Vaccines from viruses are produced.

2. Biological warfare

Genetic engineering can help humans to produce biological weapons i.e. Anthrax and Vibrio cholera

3. Agriculture

• It is common for farmers to select and plant seeds from the healthiest and high yrelding varies of plants with the aim of improving desirable traits as high fruits and crop production.

• Also genetics has enabled the begining of selective breeding. Selective breeding is the crossing of animals or plants that have desirable traits to produce offspring that have a connection of the parents’ desirable characteristics

• Also the knowledge of genetics developed in breeding which involves crossing relatively individuals to maintain desirable traits. The various breeds of cattle, dogs, pigeons, chicken and maize, sugarcan and goats are a result of in breeding

4.Genetic disorder

1. Pregnant women can be informed about the deformation of the fetus

2. It can help in the modification of disordered genes

Dangers of genetic engineering

1. The outcome of genetic engineering can be weird out of our imagination

2. Production of new pathogens accidentally or deliberately

CLASSIFICATION

SIMPLE MENDELIAN TRAINTS

The following are example of mendelion’s traints in man

1. ALBINISM

It is controlled by a recessive gene. Human showing this disor der must be homozygous recessive. Heterozygous are normal but carreer.

Examples

1. What will be the result of normal man who married an albino woman?

Solution: -

Let gene fornormal be A and Albino be a

Phenotype - all are normal (Heterozygour)

2. What would be the result of a cross between heterozygous parents?

Genotype – AA, Aa and aa

Genotypes - Aa and aa

Phenotypes - half normal/ carries and albinos.

4. What would be the result of crossed between heterozygous parent and homozygous nomal parent

         Solution:-
         Heterozygous Aa, homozygous AA

Genotypes - AA, Aa

Phenotypes - all are normal (normal, carriers)

2. ACHONDROPLASIA

Examples: -

1. What would be the result of a normal man who married an achondroplasia woman.

Solution: -

Genes for normal man - aa

Genes for achondroplasia women - AA

Phenotypes - All are anchondroplasia

Genotypes - Aa

2. What would be the result of a cross between an achondroplasia woman who is homozygous and achondroplasia man who is heterozygous?

Solution: -

- AA, Aa

Phenotypes - All achondroplasia

3. What would be the result of a cross between heterozygous parents?

Solution: -

Phenotypes - 3 Achondroplasia, 1 Normal

Genotypes - AA, Aa, aa

Phenotypic ratio - 3: 1

Genotypic ratio - 1 : 2 : 1

3. HAEMOPHILIA

It is controlled by recessive gene. Heterozygous are normal/carries but homozygous individuals are haemophilic.

Worked example: -

If a norman man married a haemophilic woman, the offsprings would be

Solution: -

Let genotype for the man X ^HY and woman X ^hY ^h

· A haemophilic man will be X ^hy

· Haemopholic female will be X ^h X ^h

· H – not suffering from haemopholic while h – haemopholic

4. COLOUR BLINDNESS

Is the hereditary trait characterized by inability to detect certain colours of the spectrum. The common colour blindness is inability to distinguish between red from green.

It is controlled by a recessive gene. Homozygous individual are colour blind while heterozygous are nomal or carrier.

e.g . If a colour blindness man marries a nomal woman, the offspring will be as follows.

Let B – normal

b - Colour blind

1. SICKLE CELL DISEASE

It is controlled by a Recessive gene. Homozygous individuals are sickled cell while heterozygous individuals are normal/ carriers.

NOTE:

HbA –

HbS

* If a carrier man marries a carrier woman the offsprings will be

- perfect normalv

- sickle cell trail

- sickle cell anaemia

6. TONGUE ROLLING

TRAITS/ DISORDERS AND THEIR CONTROLLED GENE

DOMINANT GENE

RECESSIVE GENE

Achondroplasia

Haemosphilia

Tongue rolling

Colour blind

Night blindness

Sickle cell

Brown iris

Blue iris

Having more than 5 fingers & toes

Normal night vision

Albinism

Normal number of finger and toes.

HOW TO SOLVE GENETIC PROBLEMS BY USING PUNNET SQUARE

Solution: -

i) Let letter A - dominant gene

a - recessive gene (albinism)

• Write the genotypes of the parents

(male) aa x Aa (female)

ii) Use these genotype to complete the punnet square

iii)Summarize the genotypic and phenotypic ratios

Genotypic ration - Aa : aa = 1Aa: 1aa

Phenotypic ration - ½ normal skin pigmented : albino = 1:1

Solution: -

1. Write complete/partial parents genotypes and offspring

Parents A

Four nomal skin offspring A

Since normal skin is dominant, each of parent and 4 children must have at least one dominant gene

2. Since albino gene is recessive, 2 albino offspring are homozygous recessive (aa)

Two albino offsprings (aa)

A - (Normal skin parent)x A - (normal skinparent)

A - (4 normal offspring aa - (2 albino offspring)

Since one gene for albino comes from each parent. Therefore each parent is heterozygous (Aa)

RHESUS FACTOR

About 85% of the human population has a gene located on the chromosomes number one that produces a function protein called ANTIGEN & (Rhesus factor)

Individuals with rhesus factor are rhesus positive (Rh⁺) and the remain 15% do not have this factor are rhesus negative (Rh^-). Rh⁺ is dominant over Rh^-.

The table below shows the reactions of blood types with and without Rh factor.

KEY: (√) - No agglutination

(x) - Agglutination

WORKED EXAMPLE

A Rh⁺ man marries a woman who is Rh^- and produces 10 children, what will be the phenotypes of the children

SEX INHERITANCE

· In many species female chromosomes (sex) are XX and male are XY

The chromosomal mechanism of sex determonation varies in different organisms

Example: -

Organisms

Gametes

Zygotes

Ova

Sperm

Female

Males

Drosophila, Human beings, Grasshoppers, Birds, Moths, Butterflies

SEX DIFERENTATION IN HUMAN BEINGS

• The embryonic gonads which develope consist of 2 parts

1. Cortex - an external layer developing to ovary

2. Medulla - an internal layer develoing to testes

• In addition there are 2 ducts in the neutra embryo

1. Mullerian duct which persist if indivudual becomes a male.

2. Wolfian duct persist if the individual becomes a male

After the neutral stage, specific sex determiners take over and stimulate the development of sex organ that are either male or female.

If the embryo’s chromosomes is XY the medula part enlarges and begins to differentiate while cortex portion disappears.

If the embryo is XX the cortical/ cortex portion develops while the medullary part disappears.

SEX LINKAGE

Sex linked genes carried on sex chromosomes but have nothing to do with sex. Traits whose expression is governed by sex linked traits are called sex linked traits .

One kind of colour blindness is an example of sex linked trait in human beings located on the X – chromosome. Example of other linked are haemophilia (bleeder’s diseases).

VARIATION

Variation is the possession of characteristics which are different from the parent and other offsprings.

Types of variation.

1. Continuous variation

Is the variation which show intermediate form between any two extremes i.e there is no clear cut distinction between two extremes.

Example in group length ranges from shortest to tallest with several intermediaries continuos variation arises from interaction between genes and environment.

2. Discontinuos variation

Is the variation which show clear cut distinction from one form to another form.

Example: -

In human population an individual is either a male or a female, ability to roll the tongue, albinism, blood group (A,AB,O) and rhesus factor.

Environment does not influence the characteristics that show discontinuor variation.

Example blood group can not be altered by environment.

Cause of variation

1. Environment Factors

2. Genetic factors

(a)Meiosis – during meiosis there is segregation of different gametes.

· This reduces the chance of pairs of chromosomes producing a wide variety of different gametes. This reduces the chance of individuals being the same.

(b) Fertilization – during fertilization the nuclei of male and female gametes fuse.

· This permits parental genes to be brought together in different combinations.

· This may lead to desirable and undesirable qualities of parents be combined in the offspring.

3. Migration

TYPES OF CHARACTERS

1. Acquired characters

These are traits an individual develops as a result of adaptation to the environment. Example: - Walking style. They are never inherited and are also know as no-heritable characteristics

2. Inherited characters

Are traits passed on from parents to the offsprings through sexual reproduction.Are also called heritable characteristics.

Difference between acquired and heritable

ACQUIRED CHARACTERISTICS

HERITABLE CHARACTERISTICS

1.Are due to the environment

2.Can not reappear in offspring.

3.Sometimes are changable in life time (one way lose weight)

1.Are due to genes

2.Re-appear in offsprings

3.Mainly unchangable in life time (height

MUTATION

Mutation are changes in the genetic material in the gametes.

• It includes appearance of new characters that have never been before in that population

• Individuals who undergone mutation are called Mutants

•Mutation can be due to

1. Change in a gene itself

2. Change in arrangement of genes

3. Loss of chromosomes (due to unbalanced meiosis)

• Mutation can be caused by agents known as Mutagens

§ X-rays

§ Cosmic rays

§ Heavy metal (lead & mercury)

TYPES OF MUTATION

1. Gene mutation

2. Chromosomal mutation

1. GENE MUTATION

Gene mutation occurr as a result of altering the chemical structure of genes

• There is a change in the sequence of nucleotides is the segments of DNA coresponding to one gene. This inturn alters the sequence of amino acids required in synthesis of a particular protein.

• The protein formed will be different from the normal ones and produce a profound effects on both the structure and development of an organism Example: sickle cell, dwarfism.

TYPES OF GENE MUTATION

1. Substitution

2. Insertion

3. Deletion

4. Inversion

i. SUBSTITUTION

This is the replecement of one or more portions of a gene with a new one. E.g. A thymine (T) on ATA on the DNA molecule is replaced by cytocise (C) and result to ACA on the DNA

This is examplified in sickle cell anaemia only one nucleotide is changed. This kind of mutation involving the change of one nucleotide is called Point Mutation.

ii. INSERTION

A portion of DNA strand cuts and rotates through 180° the invesion results in alteration of the base sequence at this part.

Example: -A base triplet CTA can have its base thymine (T) and Adenine (A) cut and rotated. The result is CAT which is different from amino acid.

2.. CHROMOSOMES MUTATION

TYPES OF CHROMOSOME MUTATION

1. Deletion

2. Duplication

3. Inversion

4. Translocation

5. Non-disjunction

6. Polypoidy

1. DELETION : This occurs when a portion of the chromosome breaks off and fails to reconnect to any of the chromatids, The result is the loss of genetic materials.

Deletion can be caused by error in chromosomal crossover durin meiosis. These causes serious genetic deseases

       2. DUPLICATION
             This occurs when a portion of the chromosome replicates itself adding extra length. The result is addition of a set of genes which is a duplication

This may result to over emphasizing of a trait in an organism.

    3. INVERSION
        This occurs when a middle piece of the chromosomes breack and rotates at 180° and rejoins the chromatid. This has the effect of reversing the gene sequence.

4. TRANSLOCATION

5. NON-DISJUNCTION

Example of non – disjunction

(a) DOWN’S SYNDROME

This is caused by presence of an extra chromosome number 21 individuals with this defect have a total of 47 chromosomes they have

· Resistance to infection

· Mentally retarded

· Have thick tongue

· Short body

Also children of old parents (above 40 years woman and 55 man) have increased chance of Down’s syndrome.

(b) KLINEFELTER’S SYNDROME

6. POLYPLOIDY

Occurs if the whole set of chromomes doubles after fertilization, where the spindle fail to be formed and the cell does not divide.It is rare in animals but common in plants

7. SICKLE CELL ANAEMIA

Sickle cell anaemia is an example of gene mutation. The normal haemoglobin is entirely replaced by an abnormal haemoglobin known as haemoglobin S

In sickle cell anaemia, the glutamic acid is replaced by another amino acid, the valine forming a haemoglobin s denoted by Hbs. Normal haemoglobin is denoted by HbA.

Haemoglobin S begins to crystallize when Oxygen concentration falls and causes red blood cell to assume the shape sickle. Half the number of red blood cell is sickle

GENETIC COUNSELLING

Genetic information is used to advice couples who have hereditary disorders about chances of children inheriting the disorders. Genetic information could also be used in choosing marriage partners.

GENETIC ENGINEERING

This is the alteration of the structure of DNA by man.

• Genetic engineering enables man to carry out reseach.

§ Manufacture protein (insulin)

§ Improve animal and plant breeds

§ Correct genetic disorders

APPLICATION OF GENETICS

1. MEDICINE

• Human growth hormone ha also been made by using bacteria which the proper gene has been added.

• Also blood cloting factors such as fibrinogen needed by haemophiliacs are produce.

· Vaccines from viruses are produced.

2. Biological warfare

Genetic engineering can help humans to produce biological weapons i.e. Anthrax and Vibrio cholera

3. Agriculture

• It is common for farmers to select and plant seeds from the healthiest and high yrelding varies of plants with the aim of improving desirable traits as high fruits and crop production.

1. Pregnant women can be informed about the deformation of the fetus

2. It can help in the modification of disordered genes

Dangers of genetic engineering

1. The outcome of genetic engineering can be weird out of our imagination

2. Production of new pathogens accidentally or deliberately

ORGANIC EVOLUTION

CONCEPT OF ORGANIC EVOLUTION

Organic evolution

Is the gradual developent of organisms from simple life forms to more complex life forms over the course of time. Evolution answers the question why do organisms show such great diversity/ difference. Also evolution is the process of change by which new species are formed from pre-existing species.

The main theory/ idea of evolution is that population of living things do undergo changes over generation. According to this theory some organism resemble each other hence they have a common ancestor e.g Human being and Primates, Donkeys and Zebra.

Importance of organic Evolution

1. Results to the emergence of new species from pre- eisting ones (the new species are able to adapt to the changing environmental factors as climate, food)

2. Organic evolution can modify some of the body structures of the organisms to match the need of the environment

3. Organic evolution can modify immunity system to increase the survival value

ORIGIN OF LIFE

It is believed that Earth formed around 4.54 billion (4.54×109) years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere, but it contained almost no oxygen and would have been toxic to humans and most modern life. Much of the Earth was molten because of extreme volcanism and frequent collisions with other bodies. One very large collision is thought to have been responsible for tilting the Earth at an angle and forming the Moon. Over time, the planet cooled and formed a solid crust, allowing liquid water to exist on the surface

The first life forms appeared between 3.8 and 3.5 billion years ago. The earliest evidences for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Photosynthetic life appeared around 2 billion years ago, enriching the atmosphere with oxygen. Life remained mostly small and microscopic until about 580 million years ago, when complex multicellular life arose. During the Cambrian period it experienced a rapid diversification into most major phyla.

THEORIES OF THE ORIGIN OF LIFE

There are four theory of origin of life which are the following

1. Special creation

2. Spontaneous generation

3. Steady state

4. Organic evolution (scientific evolution)

1. Theory of special creation

According to this theory life was non existent before a particular time then the supreme being super natural father created all living things and there was life on earth. These theory are found in holly books.

2. Theory of spontaneous generation

Scientists believed that from non living matter living matter developed Example; Worms and frogs could have come from mud dut or rotten food

This theory was applied up to the 19^th century but nolonger applied

3. STEADY THEORY

These theory they don’t explain the origin of the planet, earth and all organisms. Say people found life with no source.

4. Organic evolution (scientific theory of evolution)

It states that life probably started by a catality effect that made free elements to combine to form molecules. Elements combined by a catalytic effect probably lightning, ultra violate radiation or possibly gamma rays. The first four gases to form were ammonia, hydrogen, water vapour and methane.

This theory was supported by Stanely Miller who used an electric spark to synthesize amino acids from the above four mentioned gases

These molecules further combine to form a stable system capable of releasing energy and replicating its self these were the first living organisms resembling the present day viruses and bacteria more complex organs develop later.

Origin of species

It is the process by which new species were formed from pre existing ones

Causes of origin of spieces

The deme of the organisms were not distributed evenly on the land they were isolated due to natural disasters or behavior changes these isolations were the causes of orgin of new spieces

Isolation of mechanisms

Reproductive isolation

This is caused by such changes that bring about barriers to successful mating between individuals of the same species

Ecological isolation

These are environmental barriers that keep population or demes apart. These barriers make demes occupy different types of habitant from the original type

Geographical isolation

These are physical barriers such as ocean, seas, mountains, ice valleys etc. These geographical barriers prevent the organisms from exchanging their genes

Behavioural isolation

This is the change in the behavior before matting period i.e Courtship or nesting

The prospective changes take place if fertilization occurs

Evidence of origin of evolution
                1. Fossil records
                2. Cell biology comperative embryology
                3. Comperative anatomy
                4. Comperative physiology

1. Fossil record

Fossil are remains of the organisms that lived in ancient times. The age of a specimen can be determined by the weight of the carbon in that specimen e.g.

A fossil containing 5g of carbon showing the organism had been 5600years old. Arthiological discovery showed that homonity family which humans belong. The pongitae family to which apes like chimpanzees and the gorilla belong arose from premate stock called proconsul as per arthiologist evidence the earliest homoninids appeared about four million years ago. They were not having culture of tools making and fire making. From the same family genus homo are some development and changes to homo habilis.

Homo habilis used tools and became extinct about 1.5 million years ago.

The next species emerged were homo erectus the organism which was able to stand in an erect position homo erectus was showing communal life and work fire and toll making.

The present days specieces are homo sapiens or rationalizing man which was behaving high intellectual capacity ability to communicate through languages ability to show many skills

2. Cell biology

All the cells of higher organisms show basic similarities in their structure and function i.e. all cells have DNA as carrier of genetic information. All use roughly the 20 amino acids to synthesis protein and all use the ATP as energy carrier the fact that all cells have the cell membrane, ribosome and mitochrondria etc which perform similar functions indicate that all organisms had a common ancient origin.

These are other structures and chemical substances that are confined to specific groups of organisms. Organisms sharing the same chemical characteristics are considered to be more closely related this principle has been recently used to confirm phylogenetic relationship this principle is known as biochemical homology

e.g. of biochemical homology

· most plants contain chlorophyll, cellulose and starch which are absent in animal tissues

· verterbrates are the only animaks that posses adrenaline and thyroxine

· only algae posses orange pigment called fucoxanthin

3. COMPARATIVE EMBRYOLOGY

These is the branch of embrology that contract and relate the embryo of the different species. It help to show how all organism relate. Many living thing are compared. Wheather or not organism have a notachord or not , it has gill arches. Many things go into comperative embrology and many thing can be included

Comparative anatomy

Organisms with basic structural similarities have a common related ancenstral. Based on the structural similarity their functions anatomical studies are divided into :

1. Homologous structures

These are structures that perform different functions though they have similar ancenstral origin

Examples :

Beak structures in birds

Feet structures in birds

Limb structure in vertabrates

The type of evolution where by organisms with similar ancestral origin develop structures that form different functions is called dibergent evolution

3. Analogous structures

These are structures that perform similar functions though they have different ancestral origin

Examples: Wings in birds and insects , Eyes of the human and octopus

Convergent evolution

This is the type of evolution where by organisms with different ancenstral origins develop structures which appear similar in the form and structure

Vestigial structures

These are structures which are developing from generation to the next but they serve no use. Example; appendix in humans, wings on flightless birds like the ostrich

4. Comparative physiology

Due to continental drifting organisms with a common ancestral origin became isolated and hence evolved into different species examples; monkeys with long tails found in the amazon while monkeys with short tails found in the African continent.

Mechanism of evolution

These are many theories to explain possible machanism of evolution

1. Lamarck’s theory

2. Darwin’s theory

3. Neo darwin’s theory

4. Punctuated equilibrium theory

1. Lamarck’s theory

Larmack led to the principle of natural use and disuse of structure. He observed that the more an individual used a part of his body the more developed that part became

If an individual failed to use a particular part that part became weak and finaly disappeard Lamarck concukded that the giraffe developed a long neck due to its use while the flight less birds had their wings reduced and function less due to their dis use

Lamarck proposed that these changes of structure acquired during the life time of an individual were transimitted to their off springs which resulted into the emergency of new species

Merits in Lamarck’s theory

According to Lamarck an individual is able to develop structures to suit the need of the environment it increases the organism survival in the diverse environment

Demerits in lamarcks theory

Modern genetis tells that the phenotypically acquired characteristics can not inherit therefore lamarclk’s cannot explain the emergency of the new species

2. Darwing of the theory

Charles Darwin proposed three theories

1. Natural selection

2. Struggle for existence

3. The survival for the fittest

Merits of darwin’s theory

According to Darwin a number of species tend to remain constant all the time due to the regulating factors such as food, disease and predation etc.

Demerits

· Dawrin theory did not explain how changes occurred by chance.

· He was not able to explain how transmission of the traits occurs

3. Neo Darwin theory

These are theories that arose after Darwin theories. It said the processes of evolution can be traced to changes that take place due to mutation.

Mutation brings changes which can pass to the next generation which leads to the emergency of new species

4. Punctuated equilibrium theory

This theory was put forward by Stephen gould and the niles elddredge they proposed a specie remain stable for long time [ equilibrium] but often sudden and un predictable changes spring up punctuated giving rise to new structures and new species

EFFECT OF ORGANIC EVOLUTION

1. Sickle cells anaemia

Is the hereditary disorder in which the red blood cells assume a sickle cresent shape making them less efficient in the transportation of oxygen. People with sickle cell traits are more resistant to malaria than normal people

2. Resitance to insectsides and drugs

There are some organisms that develop resistance to chemicals such as insecticides and antibiotics in continued use. Examples; DDt mosquitoes, penisilin and bacteria

Melanin pigmet

There are some organisms that occur in two or more distinct forms which is known as polymorphism. Examples of polymorphism is prepared moth which occurs in white form and melamine form or dark form

The moths are normaly found on the trunks of branches of the trees where they camouflage against predators.

In the population of the melanine due to the environmental pollution because of the darkened tree tranks and branches which makes them less subject to predation population white moths are decreasing

Factors that bring about evolution

Evolution on living organism are brought about by various thing such as :

1. Mutation

2. Migration

3. Environmental changes

4. Crossing over

5. Artificial selection

HIV

HIV

HIV stands for human immunity deficiency virus. HIV weakens the body immune system by entering into white blood cell (lymphocytes) and binds itself to chromosome and integrates into the genetic material. The virus now multiplies very fast using genetic materials of WBC. The daughter virus invades WBC destroy and kill them. As more WBC is killed the body becomes less and less fight against disease. Patient with aids are prone to opportunistic infection caused by fungi, bacteria and protozoa.

In nutshell people with AIDS die with disease their body cannot resist. These diseases are referred to as opportunistic infection. E.g. tuberculosis, severe diarrhoea, skin cancer and pneumonia.

AIDS

AIDS stand for; Acquire Immune Deficiency Syndrome. For someone with AIDS T-helper fall below.

the T-helper count for health person range between 450 and 1200

CAUSES

AIDS is viral infection caused by a strain of a virus called HIV. HIV means Human Immunodeficiency Virus. HIV mainly found in body fluids such as blood, semen and vaginal secretion. Also traces of HIV found on saliva, tear and sweat

1. Primary stage (window stage) : It does not show any symptoms except for slight flu HIV test result is negative

2. A symptomatic stage : Has no symptoms but the HIV test is positive

3. Full blown aids : Where by one gets various opportunistic infections and diseases

SEXUALY TRANSMITED INFECTION

These are infection, which are transmitted through sexually contact during sexually intercourse. Sexually transmitted disease are also referred to as venereal disease

RELATIONSHIP BETWEEN HIV, AIDS AND STD’s

· HIV is sexually transimitted. Having STDs can increase risk of acquiring and transimiting HIV.

· Some STI’s such as chlamydia cause open sores in the skin and become exit point into and from the brood stream of HIV.

· Studies show that infected people to be affected with another STI’s are three to five times more likely to to transmit the virus through sexualy contact.

SYMPTOMS OF HIV AIDS

· Loss of body weight

· Diarrhorea for longer than a month

· Shortness of breath

· White layer in the mouth and in the throat

· Swollen glands especially in the neck

TRANSIMISSION OF HIV

HIV is transmitted via body fluids such as blood, breast milk, vaginal secretions, sweat, saliva, tears. The most common ways of HIV transmission are:

1. Sexual intercourse with an infected person

2. Blood transmission from a infected donor

3. Organ transplants from an infected donor

4. An infected mother to her child during pregnancy birth or breast feeding

5. Using unsterilized surgical or skin piercing instruments, such as scalpels, needles and circumcision blades that have been used on an affected person

6. Sharing toothbrushes, shaving blades or nail cutter with infected person.

NOTE: HIV is not spread by casual contact such as hugging, shaking hands, or touching unless both people have bleeding wounds

Effects:

· They causes death

· Increase a poverty

· Increase the problems of orphans and street children

· It led to stigmation among society member

· People with HIV and AIDS get opportunistic infections and disease, for example: -

1. Chest infections e.g. pneumonia, TB

2. Brain infections leading to mental confusion, severe headache and fits

3. Stomach or gut infections leading to severe diarrhea

4. Skin cancer i.e. Kaposi sarcoma

PREVENTION AND CONTROL OF HIV/ AIDS

1. Avoid promiscuous sex partner prostitutes, commercial sex workers (avoid irresponsible sexual behavior abstain from sexual intercourse (if not marriage) be faithful to one sexual partner, use condom during sexual intercourse

2. Wear disposable gloves when touching peoples body fluid

3. Use sterilized instruments during surgery, circumcision and delivery

4. Only screened blood and organs should be used for transfusion and transplants

5. Go for HIV test in order to know your status

6. Do not share tooth brushes and shaving blades

7. People with HIV and AIDS should be given Anti—retroviral drugs (ARVS) which help them to show down infections.

8. Pregnant women should attend pre natal clinic where they can be treated to prevent mother to child transmission

9. HIV positive mother’s should not breast feed their new born babies

10. Follow the ABC rule,(Abstain, Be faithfull and use Condom)

CARE AND SUPPORT FOR PEOPLE LIVING WITH HIV AND AIDS (PLWHA)

People with HIV and AIDS can live health live for a long time if they get proper care and support we can care for them and supported them in the following ways:

· Give them well balanced meals in adequate quantities.

· Allow them to rest when they feel unwell.

· Taking them to a health centre as soon as they start developing signs of illness.

· Provide them with ARVS, allow them to work.

· Behaving in a loving way towards them and listen them.

· Counseling them to stop behavior that worsen

· Not discriminating against them or stigmatizing

· Hiding them from the public, denying them education or health services

· Chasing them away from home

· Refuse to share utensils or rooms with them

· Care and support gives PLWHA hope, good health piece of mind, long life strength to work and comfort.

· Discrimination led to depression, loneliness, loss performance at work and school.

IMPORTANCE OF HEALTH CARE FOR STI’s, STD’s AND OPPORTUNISTIC DISEASES

· Early testing and treatment will help to treat or slow down the development of the infection or disease in its early stage

· Proper treatment can save life and prevent long term effects such as infertility

· Healthcare professionals can give appropriate counseling on how to manage the infections

· Testing gives peace of mind

· Proper health care reduces the chance of infecting other people.

VOLUNTARY CANSE (VCT)

It is a process that is undertaken when a person wants to find out if they are infected with HIV. Because it is voluntary, a person who thinks they might have HIV decides on their own whether they want to have the test done. If the individual decides to go ahead with the tesing they will have the opportunity to discuss the test with a trained counsellor.

Most clinic use a rapid accurate scientific test that makes the results available, usually within twenty minutes after the test has been performed.

Voluntary Counselling and Testing (VCT) for HIV is an efficient internationally recognized approach for people to find out their HIV status at VCT centers. It has become one of the most effective and popular ways of diagnosing people who may have been exposed to the virus or who have been infected.

VCT is an important tool for preventing the spread of HIV—especially in communities where the epidemic is widespread. It allows for adolescents to find out their own HIV status in order to evaluate their behaviour and its consequences.

VCT clinics usually have 45 minute counselling sessions that provide information about HIV and AIDS and the testing process. VCT provides a confidential and non-judgmental environment for people who want to know their HIV status.

VCT can help to improve advocacy and reduce stigma by giving people the opportunity to talk anonymously and confidentially with counsellors about their HIV status.

Voluluntary councelling and test involve pre testing counseling and post testing counseling.

Pre testing counselling is done in advance before HIV test

Post testing counselling is done after HIV test if it is positive.

There are Three Main Steps in VCT:

First, there is a session of pre-test counselling where questions about HIV/AIDS and the test are discussed and answered by a counsellor. The counsellor will help the individual determine whether testing is appropriate given the information that is shared with them about the reasons the individual wanted to be tested. Sharing information about their past sexual behaviour will help the counsellor determine whether testing is appropriate. After making their assessment, if the counsellor deems it appropriate for the person to take the test they should

1. Describe the test and how it is performed

2. Explain AIDS and the way HIV infection is spread

3. Discuss ways to prevent the spread of HIV

4. Explain the confidentiality of the test results

5. Discuss the meaning of the possible test result

6. Ask what impact you think the results of the test will have on you

7. Discuss whom you might tell your results to

8. Discuss the importance of telling your sex and/or drug-using partner(s) if the results come back positive

Second, when the person decides to have the HIV test they must sign a consent form before the test can be administered. Informed consent is a crucial part of the VCT process and it is important that the individual is aware of their right to refuse any medical procedure, to be informed about it, and to agree to it. There is a statement which they should be asked to read beforehand stating that they have been informed about the HIV-antibody testing procedure, that they understand, and have given their consent to have the test performed.v

Finally, after the test has been done the counsellor gives the results to the person in the post-test counselling session (it usually takes around fifteen to twenty minutes after the test has been administered for the results to come back. If they are found to be HIV-positive (meaning that they have HIV) then they are referred to medical specialists and other counsellors in order to aid them in receiving treatment and support.

WHO SHOULD SEEK VCT SERVICES

1. Anyone who has been exposed to the risk of sexual behavior.

2. Anyone who is seriously considering changing his / her sexual partner

3. Anyone who is diagonized with sexually transmitted infections

4. Anyone who has had/has more than one sexual partner

5. People who are sharing sharp instruments

6. Commercial sex workers

7. Refugees and migrant workers

8. Anyone who wishes to find out his /her sexual partner

SIGNIFICANCE OR IMPORTANCE OF VCT

1. It is a way to find out about HIV and AIDS status so that a person can plan for the future

2. It is an effective way of preventing HIV and AIDS because it promotes sexual behavior change and helps people to make wise decisions

3. It is a means of HIV and AIDS treatment and care

4. It helps people to get useful and right information about HIV and AIDS

5. It provides psychological support for people living with HIV and AIDS thus helping them to lead a normal life

6. It helps the government in planning for care and treatment by knowing the number of infected people

7. Testing negative is a strong motivation for one to reduce sexual behavior

8. Testing positive gives one an opportunity to find out how he / she can live longer and a more productive life

9. It gives confidence to the people that are planning marriage or pregnancy

10. It helps to prevent mother to child transmission

Some barriers to VCT for young people

1. Some of the barriers to VCT for young people include limited availability, legal issues and accessibility of VCT services.

2. Waiting times and costs

3. Pressure by health staff to notify partners

4. Worries about confidentiality and fear that the results of HIV tests would be shared with partner(s) and/or parent(s) without their consent.

5. Fear of being stigmatized and labeled by their friends, families and communities.

6. Inadequate prevention, care and support from health care providers (i.e. councilors, doctors, nurses etc.) to effectively meet the needs of youth.

PROCEDURE AND TECHNIQUES OF VCT

· Counseling and testing must be truly voluntary

· The counselor should cross check code numbers on all forms against the client codes

· The results should be provided to a person in person to ensure that the correct person receives the results this also helps to maintain confidentiality

· The counselor should ensure the person has enough understanding of the results

· The result should be provided in the manner that it is easily understood by the client if the result is positive the counselor should be gentle and provide emotional support so as to help the client cope with the situation

· When the client is negative the counselor should provide information on how to remain negative

· It is better to provide pre testing counseling and guiding

· The counselor should be aware in the manner he /she calls clients from the waiting area to avoid verbal or non verbal behavior that might disclose the status of the client and he can be mentally distressed

· Unless it is very necessary result should not be provided in written form

· The results should not be given if the client is not ready to accept them

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