Gregor Mendel (1822 – 1884) is considered the father of

genetics. He was an Austrian monk who studied and taught

Natural science and Mathematics.

Mendel is famous for the experiments he performed on pea

plants. He chose the pea plant because the flowers are SELF-POLLINATING – pollen from

a pea plant lands on the stigma of the same flower and fertilizes itself. Also, pea plants could easily be

CROSS-FERTILISED artificially to produce a HYBRID. Hybrids are new types of plants formed by cross-

fertilising different varieties of the same species.

He first grew many varieties of pea plants – making sure that each of these plants was PUREBRED – that is

when it pollinated itself, succeeding generations always looked like the parent plant. Then Mendel began

to cross purebred plants that differed in only one characteristic such as height. He called this cross a

MONOHYBRID CROSS. He always chose contrasting traits – height of plant (tall or dwarf), shape of seed

(round or wrinkled) – colour of seeds (Yellow or green).

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To cross two plants, he and his helpers spread pollen from the stamens of the plant with one trait, such as

a dwarf plant, onto the stigma of the plant with the opposite trait, such as a tall plant.

When the seeds developed – Mendel planted them and recorded what the offspring looked like. He carried

out his experiments over 8 years and recorded results from over 10 thousand different plants. The

Scientists from that time thought that the characteristics of both parents blended together

Based on the his investigations, Mendel proposed 3 laws of inheritance collectively known as Mendel’s

Laws of Inheritance as summarised below:

1. LAW OF DOMINANCE: dominant ‘factor’ masks the recessive one.

2. LAW OF SEGREGATION: During formation of gametes, the paired ‘factors’ segregate/separate and

each gamete receives one of the ‘factors’.

3. LAW OF INDEPENDENT ASSORTMENT: factors which control different characteristics (different genes)

such as height of the plant and colour of the seed segregate randomly and independently of each

other during gamete formation.

4.

Later discoveries in 1870 – threadlike structures found in the cell nuclei – named CHROMOSOMES.

Chromosomes believed to carry the hereditary “factors” that Mendel had referred to. The “factors” were

named GENES.

We now know that there are many genes in each chromosome. Geneticists think

that there are about 25 000 genes on the chromosomes in each human cell. A

GENE is a small piece of DNA in the chromosome which carries information about a

particular characteristic in our body and is the unit of inheritance.

Each gene is found in a

particular position or LOCUS

on a chromosome. The

different forms of the same

gene is known as an ALLELE. It is found in the same

position on the corresponding homologous

chromosome. One allele comes from the mother and

the other from the father. The set of all genes in any

population of a particular species is referred to as the

GENE POOL.

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FILIAL GENERATION refers to a generation in a breeding

experiment that is successive to a mating between

parents of two distinctively different but usually

relatively pure genotypes. Often referred to as F1 or F2

depending on the generation.

A GENOME is an organism’s complete set of DNA,

including all of its genes. Each genome contains all of the

information needed to build and maintain that organism.

In humans, a copy of the entire genome—more than 3

billion DNA base pairs—is contained in all cells that have

a nucleus.

If the alleles for a particular characteristic are the same ie they both code for curly hair the organism is

HOMOZYGOUS for that characteristic. If the two alleles are different – one codes for curly hair and the other

for straight hair – the organism is HETEROZYGOUS for that characteristic. (is also known as a HYBRID)

One of the alleles in a heterozygous genotype may be DOMINANT and that characteristic will be visible in

the phenotype eg Brown eyes are dominant to blue eyes. If a person is heterozygous for eye colour (has a

brown and a blue gene – then they will always have brown eyes. The blue eye allele is a RECESSIVE gene –

you will only have blue eyes if BOTH your genes code for blue eyes.

The genetic representation of the alleles is known as the GENOTYPE. There are 3 different forms of

genotypes:

• HOMOZYGOUS DOMINANT: both forms of the gene in the allele are dominant: BB (represented by 2

capital letters)

• HETEROZYGOUS DOMINANT: one version of the allele is dominant, and one version is recessive, the

dominant gene will mask the effects of the recessive gene, and the genotype is said to be

dominant, but because there are 2 versions of the allele – it is said to be heterozygous.

(represented by 1 capital letter, and 1 lower case letter - Bb). This individual will be known as a

CARRIER of the recessive gene.

• HOMOZYGOUS RECESSIVE: both genes in the allele are recessive. As there is no dominant gene to

mask the effects of the recessive gene, the recessive gene will be visible in the appearance of the

individual. The genes are both represented by lower case letters – bb).

The outward appearance of the characteristic is known as the PHENOTYPE. Eg: brown hair, tall, spotted

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To understand how characteristics are inherited, we draw genetic diagrams. A genetic diagram shows the

genotypes and phenotypes of a cross between two parents. GENOTYPE refers to the genetic factors present

in an organism. PHENOTYPE refers to the visible expression of the genotype – the way an organism looks

due to its genotype.

A cross where only one hereditary trait/characteristic is investigated at a time, is known as a MONOHYBRID

CROSS.

In genetic diagrams we use the following symbols:

1. Generations are represented by P1 F1 and F2.

P – parent generation

F1 - (1st filial) – first generation of offspring

F2 - (2nd filial) – second generation of offspring

2. Alleles of a gene are represented by capital and small letters. The first letter of the dominant trait is

chosen as the symbol eg tall is dominant to dwarf in plants therefore: T – tall plant, t – dwarf plant.

3. As there are two alleles for each characteristic, one on each chromosome in a homologous pair, we

write two letters. The dominant allele is always placed first:

❑ Purebred (homozygous) tall plant TT

❑ Purebred (homozygous) short plant tt

❑ Hybrid (heterozygous) tall plant Tt

4. When meiosis takes place during the formation of gametes, the homologous chromosomes separate.

Each gamete receives only one allele of a pair. If the pair is made up of different alleles, such as Tt, then

the gametes receive either a T or a t.

5. The easiest way to see how the gametes can recombine is to draw a PUNNET SQUARE.

The diagram that follows is the result of crossing a homozygous tall plant with a homozygous dwarf plant.

The F1 generation were allowed to self-pollinate to produce the F2 generation.

The two HETEROSOMES (also called GONOSOMES) carry information

that determine whether offspring will ultimately be male or female.

The female chromosome (X) does not EVER swop information with

the male (Y) chromosome. This means that the information

pertaining to the sex as well as the secondary sexual characteristics

is passed on to the offspring as a complete set of information.

The male (Y) chromosome is dominant to the female (X)

chromosome, which means that all males will carry a XY

chromosome set, while all females will carry a XX chromosome set.

1

3 5 7

8

2

4

10

6

9

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Certain characteristics or genetic diseases seem to occur more often in males than in females. This is due

to the structure of the sex chromosomes. The X chromosome has many genes on it. The Y chromosome is

very short and has very few genes on it.

If a gene on an X chromosome mutates, then the mutation will be seen in the male because he only has

one gene for that characteristic, on his X. If the mutation is recessive, it will only be seen in the female if

both the X chromosomes have that allele.

This disease is caused by mutations to very large genes. Duchenne muscular dystrophy occurs when a gene

on the X chromosome fails to make an essential muscle protein DYSTROPHIN. The disease begins in early

childhood and causes progressive loss of muscle strength and bulk. People with this disease usually die in

their 20s from respiratory or cardiac muscle failure. As a result of this disorder most often being fatal in a

person’s 20’s there is little to no chance that affected son or daughter would have offspring.

If a mother that is a carrier for the gene (XDX

d

) has children with a father who does not have the gene (XDY).

Remember that this is a recessive gene and is therefore represented as a ‘d’. The punnet square look as

follows:

X

D X

d

X

D X

D X

D X

D X

d

Y X

D Y X

d Y

X

D X

D –Unaffected daughter

X

D X

d – Affected daughter

X

D Y – unaffected son

X

d Y – affected son

DO NOT ADD ANY LETTER TO THE Y CHROMOSOME SINCE THE Y CHROMOSOME DOES NOT HAVE AN ALLELE TO

COUNTERACT THE RECESSIVE ALLELE FOR HAEMOPHILIA AND COLOUR-BLINDNESS.

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Colour blindness is a visual defect resulting in an inability to

distinguish between certain colours.

It is caused by an abnormality of the pigments of the retinal

cones. When only one pigment is absent, the individual will

have a problem distinguishing between red and green. This

condition is known as red-green colour blindness and it is

the most common form of colour blindness.

The gene for colour blindness is recessive and it is carried on

the X chromosome. Men have one X chromosome, whereas

women have two. Men are colour blind if their single X

chromosome carries the recessive gene.

A woman is colour blind only if both her X chromosomes

carry the recessive gene. If a woman carries a normal

dominant allele as well as an abnormal recessive allele on her X chromosome, she will be able to

distinguish colour normally, because the dominant normal allele masks the abnormal recessive allele.

Although the woman will not be colour blind, she is a carrier of the recessive gene which she may transfer

to her offspring.

A colour blind man can only transfer the recessive gene on his X chromosome to his daughter. The

daughter will probably only be a carrier and not be colour blind herself, as her other X chromosome (from

her mother) will probably carry the dominant normal gene. If this daughter has a son, she may transfer the

recessive gene to him on one of her X chromosomes. Therefore he will be colour blind because the Y

chromosome received from his father does not carry the dominant normal gene.

If a mother that is a carrier for the gene (XBX

b

) has

children with a father who does not have the

gene (XBY). Remember that this is a recessive

gene and is therefore represented as a ‘b’. The

punnet square look as follows:

X

B X

b

X

B X

B X

B X

B X

b

Y X

B Y X

b Y

X

B X

B –Unaffected daughter

X

B X

b – Affected daughter

X

B Y – unaffected son

X

b Y – affected son

If a mother that is a carrier for the gene (XBX

B

) has

children with a father who does not have the

gene (XbY). Remember that this is a recessive

gene and is therefore represented as a ‘b’. The

punnet square look as follows:

X

B X

B

X

b X

B X

b X

B X

b

Y X

B Y X

B Y

X

B X

b – Carrier daughter

X

B Y – unaffected son

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Haemophilia is also a sex-linked disorder, but it is a more serious condition than colour blindness. It is a

condition where the blood takes a long time to clot, due to an important clotting factor. Haemophilia is a

gene mutation cause by a recessive gene on the X chromosome.

POLYGENIC TRAITS are controlled by two or more than two

genes (usually by many different genes) at different loci on

different chromosomes. These genes are described as

polygenes. Examples of human polygenic inheritance are

continuous characteristics such as height, skin colour and

weight. Polygenes allow a wide range of physical traits. For

instance, height is regulated by several genes so that there will

be a wide range of heights in a population.

MUTATIONS occur when the DNA structure of a gene changes,

forming a new allele of that gene. The change in DNA structure changes the information the allele gives to

the cell.

Mutations can either be:

❑ CHROMOSOMAL – damage to the chromosome due to UV, cosmic rays, X-rays, radiation.

❑ POINT – a single pair of nucleotides in a certain point in the DNA is replaced by a different base pair

o substitution

o deletion

o insertion

SOMATIC MUTATIONS occur in somatic cells

eg kidney, bone, skin. They may damage or

kill the cell or convert it into tumour cells

that can become cancerous. When the cell

divides mitotically. the mutation is

transferred to all the daughter cells within

the tissue or organ. Metastasis may occur

when these cancer cells spread throughout

the body. These somatic mutations die

when the cells die or when tumour cells are

killed.

GERMLINE MUTATIONS occur in eggs or

sperm. They can be passed onto the zygote

which will then have the mutation present

in every one of its cells. The next generation

of gametes will carry the mutation so it will

be passed down to the next generation.

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Some mutations may be BENEFICIAL – they may give an organism a selective advantage. Natural selection

and evolution is based on the principle that during our evolutionary history, genes mutated and formed

new alleles. These new alleles can lead to genetic variation.

Some mutations change the gene so that the allele formed

cannot function – in albinism, the pigment melanin is not

produced in the skin, hair and eyes. Some mutations change

the message a gene gives – a person can develop 6 fingers

instead of 5 (polydactylism).

Some mutations change physical characteristics but do not

effect body functioning: eye colour, tongue-rolling, ear-lobes

etc. They are HARMLESS mutations.

However, some mutations are HARMFUL. Some alleles can

cause diseases and even death. This is because the allele is not coding for the production of an important

substance that is needed either during development or in adulthood. Most of these disorders are

AUTOSOMAL RECESSIVE like sickle-cell ANAEMIA and ALBINISM. This allele is called a LETHAL ALLELE!

Autosomal disorders refer to disorders that occur in autosomal chromosomes (1 to 22). As this is not a sex-

linked genetic problem, no X and Y are used in calculating genetic probable outcomes.

A variety of letters can be used to indicate dominant and recessive alleles of genes. It is suggested that

letters that differ between capital and small case so it is clear in a punnet square which is the recessive vs

dominant. Good letters to use would be B/b; D/d; E/e etc but letters like S/s and C/c make it really difficult

to differentiate between.

Sickle-cell anaemia is a genetic disorder caused by a gene

mutation. It occurs in people in the malaria areas of

Central and West Africa as well as in the Mediterranean. In

this gene that codes for the formation of haemoglobin, the

nitrogenous base Adenine is replaced by Thymine in DNA

replication. This is a point substitution mutation. This leads

to the formation of abnormal haemoglobin (also known as

HAEMOGLOBIN S).

The abnormal haemoglobin causes the red blood cells to

become sickle-shaped and therefore they cannot

effectively fulfil their function of transporting oxygen.

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People are homozygous for these genes develop

serious form of anaemia known a SICKLE-CELL

ANAEMIA. Some for the sickle-shaped red blood cells

block the capillaries and prevent the movement of

normal red blood cells. This leads to poor blood

circulation and anaemia. People with this disease

have a very short life expectancy.

Although the person carrying the sickle-cell gene has

abnormal haemoglobin, there is still sufficient

normal haemoglobin for transporting oxygen. This person usually shows no or mild symptoms of anaemia.

This heterozygous condition is known as SICKLE-CELL TRAIT. Red blood cells with abnormal haemoglobin

(sickle-shaped) are quickly removed from the blood and destroyed in the spleen, as the body identifies

them as 'foreign'. These heterozygotes have a survival advantage in malaria areas and the mutant allele is

transferred to the offspring.

Many gene mutations are harmful, but the advantage for people who are heterozygous with respect to

sickle-cell anaemia, is that they have a degree of resistance to malaria. This is because the malaria-causing

Plasmodium multiplies in the red blood cells. Many infected sickle-shaped red blood cells are destroyed by

the body before the daughter parasites are formed or released. Therefore, these heterozygotes have a

significantly reduced chance of a serious malaria infection.

Cystic fibrosis was one of the first genetic disorders for which a lethal allele was identified. People carrying

this mutant gene cannot produce a special protein in the cells of their lungs. This protein is needed to

transport salts and water across the cell membranes into the cells. The salts and water collect in the air

passages, forming large amounts of sticky mucous that blocks the air passages to the lungs. People with

the disease find it difficult to breathe and also tend to get lung infections such as pneumonia. These

infections are usually the cause of death. Most people with cystic fibrosis die before the age of 30. In the

late 1980s, American researcher Lee-Chap Tsui discovered the position of the gene that causes cystic

fibrosis on chromosome 7. This knowledge helped doctors to diagnose the disease in children.

Cystic fibrosis is the most

widespread genetic

disease among white

people, affecting about

one in 2 000 babies. It is

estimated that one in 20

white Americans is a

carrier. Children of two

carrier parents each have

a one-in-four chance of

inheriting two defective

recessive alleles and

being born with this

disorder.

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Albinism is an inherited disease characterized by a substantially lower rate of melanin production. Melanin

is the pigment responsible for the color of the skin, hair, and eyes. People with albinism often have lighter

colored skin and hair than the other members of their family or ethnic group. Vision problems are also

common.

Melanin normally protects the skin from damage due to UV radiation exposure, so people with albinism

are more sensitive to sun exposure. They also have an increased risk of developing skin cancer as early as

the teenage years.

Genetic lineages refer to the “lines of inheritance” – or the way that the alleles of genes are passed from

generation to generation in a family. We can work out how alleles are inherited through several

generations by constructing a family tree which is also called a pedigree diagram.

A Family tree always has a KEY:

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An example of a family tree is given above which shows the incidence

Couples who would like to have children but have relatives in their families who have genetic diseases like

muscular dystrophy often go for genetic counseling to determine what the likelihood is of them having

children with the disease.

• STEP 1: a FAMILY TREE is drawn up. All the relatives over several generations are filled in with

details of who had the disease and who was clear. Once a couple know the chance of the mother

being a carrier and their future child having muscular dystrophy, they move on to the next step.

• STEP 2: The mother can go for GENETIC SCREENING. She can have her blood cells or other cells

tested using genetic fingerprinting to find out if she has the defective allele. During this procedure,

the DNA is placed in a solution containing radioactive DNA that will only attach to the gene for

muscular dystrophy. This special radioactive DNA is called a gene probe as it is used ONLY to find

the faulty gene.

• STEP 3: If a couple is at risk of having a child with muscular dystrophy, the genetic counselor will

speak to them further. They will DISCUSS the % chance of having an affected child, the effects of

the disorder on their new child, on any other children they may already have with or without the

disorder and on their own lives. They will explore all the options

available to them. The couple’s RELIGIOUS, MORAL AND CULTURAL

beliefs about termination of pregnancy will also be discussed before

attempting to fall pregnant.

• OPTIONS: After all the testing and discussions, the couple will have

THREE options;

✓ Not to have children.

✓ To start a pregnancy but abort if genetic tests during pregnancy

show that the foetus is affected.

✓ To have children regardless of the outcome. If any are affected

with muscular dystrophy, to try and give them a happy and fulfilling

life.

It is the manipulation of genes – the replacing of

defective genes with healthy alleles from another

individual OR using DNA from another organism to

produce the missing substance for the sick individual.

BIOTECHNOLOGY - is the use of plants, animals and

microbes (such as yeast and bacteria) to produce useful

products – bread and wine has been produced for

centuries using the fermentation process exhibited by

these organisms! Now scientists are using genetic

engineering techniques to alter the genetic material in

organisms to produce new and better products.

Genetically modified organisms are the result of genetic

engineering. GMOs are utilised in a variety of human

activities to improve quality of life or productivity. GMO's

may be microbes or plants or animals.

Genetic engineering affects many aspects of our lives and

our environment. It plays a role in:

• synthesis of medicinal drugs

• production of new crops

• cloning

• stem cell research

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GENE THERAPY is a medical approach that treats or prevents disease by correcting the underlying genetic

problem. Gene therapy techniques allow doctors to treat a disorder by altering a person's genetic makeup

instead of using drugs or surgery.

Gene editing is not a new development. There are a number of ways that genes can be edited by chemicals

and physical means (x-rays / radiation) however both these means are RANDOM. Biological means (CRISPR

Cas9) are new developments that are TARGETED – they can target gene specific mutations. The newest of

these is CRISPR CAS 9 (clustered Regularly inter-spaced short palindromic repeat).

Bacteria can be genetically engineered (genetically modified) to produce useful

human proteins. One advantage of using bacteria is that they can be grown in

large fermenters, producing large amounts of useful proteins.

In MEDICINE genetic engineering has been used to mass-produce insulin to treat

Diabetes, human growth hormones to help unnaturally short people to grow ... or

to give to cows to improve their milk production, follistim (for treating infertility),

human albumin (a vital blood protein), monoclonal antibodies to boost the

immune system, vaccines for treating Hepatitis B and many other drugs.

Insulin is a hormone that controls the level of sugar in a person’s blood. Diabetes mellitus is a disease where

the pancreas produces an insufficient amount of insulin. If there is too much sugar in the blood and the body

can’t use the sugar, the person could go into a coma and die. Type 1-diabetes can be treated successfully by

administering insulin injections on a daily basis. Previously, insulin was extracted in small amounts and at

huge cost from the pancreas’ of freshly slaughtered cattle and pigs.

A healthy gene allele can be “cut” from the chromosome of a healthy organism (human) and combined

with DNA from a bacterium. This DNA is called RECOMBINANT DNA. Scientists can manufacture huge

quantities of substances such as insulin for diabetics using genetic engineering. Each bacterium can

produce more than a billion copies of itself in 15 hours.

• Bacteria contain some of their genes in the form of ring-shaped molecules called PLASMIDS.

• Bacteria (E.coli) are ground and their plasmids extracted.

• RESTRICTION ENZYMES are used to

break open the plasmids.

• The gene for the production of insulin

is extracted from human DNA and

inserted into the bacterium plasmid

using an enzyme called DNA LIGASE

• Recombinant DNA is placed back into

the E.coli cell.

• E.coli multiples and starts producing

human insulin. IMPORTANT: large

quantities are produced

• Insulin is collected and purified and

used to control diabetes.

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Certain bacteria and plants can be genetically modified to produce antigens of certain viruses. ANTIGENS

are protein molecules that occur on the surface of cells and act as identifying markers. These antigens are

used in vaccines to trigger an immune response in the body. The body recognises the antigens as foreign

and produces antibodies in response. The antibodies provide immunity from infection by that particular

virus. Antigens of the Hepatitis B virus are produced by genetic engineering in yeast cells (fungi).

CRISPR CAS 9 is a gene editing tool that has been in the news a lot lately. It was found naturally occurring in

bacteria and was found to prevent the reproduction of viruses inside bacteria. Researchers are using it to

permanently modify genes to target, remove and repair mutated / unwanted sections of DNA and to

sterilize disease causing parasites

Geneticists hope to produce a

range of VECTORS to carry genes

into our bodies. One example is

using the adenovirus that

causes the common cold. This

virus is very successful at

infecting the lungs.

• The virus is made

harmless

• healthy genes are added

• and the virus is dripped

into the lungs of cystic

fibrosis sufferers

• where the healthy

genes start to begin

producing the missing

proteins.

Unfortunately, the genetically modified virus only lasts a few weeks in the lung cells before the immune

system destroys them. Scientists are still working on this as a possible cure for cystic fibrosis. The virus may

be put in an aerosol spray that the patient can inhale.

Selective cultivation/breeding of plants and animals is a natural form of genetic modification that has been

applied by farmers for hundreds of years Farmers make use of artificial selection to control the

reproduction of their plants and animals in such a way that each new generation will have most desirable

traits of the parents.

The improvement of particular qualities in a hybrid - a plant or animal produced by cross-breeding - is

known as hybrid vigour. Hybrid vigour shows the best qualities of the parents in the hybrid offspring. In

plants, cross-breeding resulted in higher yields and stronger offspring. In animals, hybrids have more of the

desired qualities required by breeders. E.g. Hybrid com has higher yields and hybrid chickens grow to a

larger size in a shorter period of time.

Genetic modification is an artificial method that speeds up this natural processes to achieve more accurate

results. In the selective cultivation of plants, genes from individual plants of the same species are

combined, while in genetic engineering any gene from any species may be transferred to a plant.

Ever since the ancient Egyptians selected wheat plants they harvested with large ears to grow their next crop

with, man has practiced selective breeding through artificial selection. Artificial selection is the process of

changing the characteristics of plants and animals by artificial means. For example, animal breeders, are

often able to change the characteristics of domestic animals by selecting for reproduction, those individuals

with the most desirable qualities such as speed in racehorses, milk production in cows, trail scenting in dogs.

The deliberate exploitation of artificial selection has become very common in experimental biology, in

genetics and microbiology, as well as in the invention and production of new drugs.

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There is no real difference in the genetic processes underlying artificial and natural selection, and the

concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural

selection. The selection process is termed "artificial" when human preferences or influences have a

significant effect on the evolution of a particular population or species. Indeed, many evolutionary biologists

view domestication as a type of natural artificial selection and adaptive change that occurs as organisms are

brought under the control of human beings.

HYBRID VIGOUR or OUTBREEDING ENHANCEMENT, is the increased function of any biological quality in a hybrid

offspring. It is the occurrence of a genetically superior offspring from mixing the genes of its parents.

Nearly all field corn (maize) grown in most developed nations exhibits hybrid vigour, or heterosis. Modern

corn hybrids substantially outyield conventional cultivars and respond better to fertilizer.

Experimental breeding of humans is considered unethical, so any evidence of heterosis in humans is derived

from observational studies. It has been suggested that many beneficial effects on average health,

intelligence and height have resulted from an increased heterosis, in turn resulting from increased mixing of

the human population such as by urbanization.

Read the following article for interest:

ARTIFICIAL SELECTION DONE NATURALLY!

CAPE BABOONS DISCOVER NEW FRUIT

12th January 2011

Cape Town - A troop of baboons has inadvertently discovered a new Minneola (citrus) cultivar for a farmer in the

Western Cape.

"Year after year the farm has been struck by a troop of baboons which descended from the mountains," van der

Merwe said. "The troop always selected one tree among thousands of trees in one of our orchards and devoured all

the fruit before our season really got going. "At closer inspection we discovered that the sweetness grade of this

particular minneola, a soft citrus variety, was much higher than the rest of the orchard and that it started bearing

fruit at least three weeks earlier than expected."

The farmers then set about grafting some shoots of this tree onto standard root stock and passed it onto the Citrus

Growers Association (CGA) at Uitenhage where the trees are now being multiplied in greenhouse tunnels. "This

process takes two years and as soon as we get the clearance from the CGA the trees will then be tested in real

orchards all over the country for a period of four years before it is officially registered," van der Merwe said.

The estate boasts the longest citrus season in the country - 10 months - and aims to produce citrus all year round

within the next four years.

"We were lucky that the baboons' acute sense of smell led them to this particular tree. It was clearly a case of a

spontaneous mutation in the orchard, which would have gone unnoticed were it not for the baboons. "I'm sure they

will have a feast one day when we produce a whole orchard of these early, sweet minneolas."

www.news24.com

In plants, every cell can grow into a new plant. So plants can be CLONED by breaking them up into small pieces

or separating the cells, and new genes can be inserted into those cells. These genetically engineered cells

can develop into new plants. The Green Revolution started in the 1970’s to try and find an answer to feeding

the world. It is estimated that there will be about 30 billion humans by 2040.

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Around the world, geneticists are working to introduce new genes into plants to make them more

commercially productive. Crops are being modified to make them more resistant to drought, insects, viruses

and herbicides (weedkillers) and to improve the quality of the crop.

1. Sugar cane is being manipulated to produce a lot more sugar.

2. Super sorghum – will be more nutritious, more easily digestible, will have higher levels of Vitamin A

and E, iron, zinc and certain amino acids.

3. Golden rice – normal rice (the staple diet of many countries) is short of micronutrients such as Vit A

and iron. Vitamin A is found in a yellow pigment called carotene in many fruit and vegetables. Genes

from carotene producing plants have been placed into rice so that Golden rice produces Vit A and

another gene to increase iron content, will help prevent anaemia in those who eat this rice.

4. Crops that repel insects – save the farmer on expensive insecticides (and reduce impact on

ecosystems). Geneticists are using a bacterium Bacillus thuringiensis (Bt) found in the soil which

produces a protein that combines with enzymes in the insects gut and forms a poison that kills the

insect. The protein has no effect on people, animals or other insects – Bt bacteria are very specific

for the type of insect they kill. Geneticists introduce the gene for these proteins into the plants these

insects like to eat. Bt cotton is grown in KZN.

5. Crops that resist viruses

– GM maize prevents viruses from replicating and spreading.

- Cassava (a staple food in areas of low rainfall and poor soils in SA)

6. Crops resistant to herbicides – used to kill the weeds that grow among crops and compete for light,

moisture and nutrients resulting in poor crops with low yields.

7. Drought resistant plants. GM maize.

8. Around the world there are about 25 – 30 different Transgenic Crops.

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Scientists have been selectively breeding to make organisms bigger and better for centuries.

With genetic engineering, comes a great debate about whether it is good or bad.

❑ Protect them against parasites

❑ Improve their productivity

❑ Enable them to grow where they have never grown before

❑ Produce new products

❑ Bring hope of medical cures

❑ Increase yields in agriculture

❑ Perhaps even provide solutions to pollution and energy issues

❑ There is a lack of trust in GM foods – we simply don’t know all the risks.

❑ Politics and Economics are involved.

❑ Not all farmers have access to the technology.

❑ Lack of sustainability – especially in Africa. Farmers can’t afford the GM grain & seed.

❑ We simply don’t know the long term effects on human health – even though the oldest existing crop

has been eaten since 1990!

❑ Contamination of wild crops is a serious threat – although tests and legislation should control this.

❑ Labelling – Until this becomes law in the new legislation, people simply don’t know what they are

eating anymore.

• The farmers – Yields are 50% higher. They don’t have to spray. Much greater production per hectare

• Consumers – More nutritious foods that are readily available most seasons of the year.

• Multinational companies - who hold the patents on GM foods and seeds eg. Monsanto.

• Better pest control

• Herbicide tolerance

• Drought tolerance

• Safer foods

• Medicine can be incorporated into foods

• GM plants can clean up heavy metals in soil

eg from mine dumps

• Improved forestry

• Improved food security

–

Polyploidy is the condition of having three, four, or more sets of chromosomes instead of the two present in

diploids, like people. In plants, the process of polyploidy sometimes results in a new species, making it an

important mechanism in evolution. Cotton, potatoes and wheat are polyploids while maize and soybeans

retain some ancient polyploidy. Fossil records show over 80% of plants may be a product of polyploidy.

Advantages of polyploid farming include crops with multiple durable resistance to pests and diseases,

particularly in the absence of pesticides. Likewise, transgenes may assist in the development of high yielding

crops, which will be needed to feed the world and save land for the conservation of plant biodiversity in

natural habitats.

Genetic engineering of food crops makes more productive crops are

not the answer to world hunger. They say world hunger is caused by

many factors such as: the inability of poor farmers to borrow money

to but seeds and equipment, the lack of storage facilities, and poor

infrastructure for transporting and selling their produce. There is

also concern that multinational companies will control seed prices

in the future, and genetically engineered seed will be unaffordable.

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Some religious and vegetarian groups oppose genetic engineering because genes from animals they don’t

wish to eat could be inserted into crops that they do eat.

Transgenic organisms can contain genes from combinations of any of the following:

• Plant and plant

• Plant or animal and

virus

• Plant or animal and

bacteria

• Plant and animal

• Animal and animal

• Animal, virus or

bacteria and human

A gene from one species is transferred to the chromosomes of fertilized eggs or ova of another species. As

the animal develops, the new gene is present in every cell of the body.

Research is in progress to turn sheep and cows into drug factories in a new research area called

“PHARMING”– the fertilized ova will be given extra human genes. As adults, they could then produce useful

proteins in their milk, such as the clotting factor IX, which is needed by people with haemophilia B. This

protein can then be extracted from the milk and used to treat haemophiliacs.

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The development of the Pro-tato - a potato with more protein per

gram compared to the normal potato has been developed using

Amaranth Albumin 1 (AmA1), which is one of the genes of

Amaranth. This gene has its own agricultural value as it is the main

gene responsible for the growth of the plant as well as for the high

level of protein and increased chains of essential amino acids. A

result of two years of hard work, this new class was developed by

inserting the gene into seven various varieties of potatoes. These

are now commercially grown as transgenic potatoes.

Atlantic salmon have been

engineered to grow almost

double the size of the wild

variety (naturally occurring) to

improve food production for

northern European economies.

The GM salmon have huge

appetites and may outcompete

the wild salmon if they are

released into the oceans.

Spider silk used as artificial ligaments and

sutures.

Surgical sutures: Most surgeons use thread or

silkworm silk to stitch wounds back together,

but spider threads are even thinner. "That’s

very important for eye or nerve surgery, where

you might want something that’s very, very

thin," Lewis says. "Spider silk is also much

stronger. We already know it will work well as

a suture."

Goats have been genetically engineered to produce

milk which is rich in spider silk, by inserting the silk

gene from orb web spiders into fertilized eggs of

goats. As the goats grow and start producing milk,

the milk is collected and processed to remove the

spider silk. This gives a much quicker and larger

supply of spider silk than collecting it from spider

webs. The product is used in the manufacture of

bullet-proof vests and artificial tendons and suture

thread. Current research is underway to produce

airbags for motorcars from this silk

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Human genes have been inserted into bacteria to produce human