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2244 GGeenneettiicc eennggiinneeeerriinngg

24.1 What is genetic engineering? (Book 3, p.236)

• (1) Genetic engineering (����) refers to the laboratory techniques which

enable biologists to change the genetic information of an organism.

• It can increase the (2) variation of species by human manipulation of genes.

The basic technique of genetic engineering (Book 3, p.236)

The manipulation of genes involves four key steps:

cell carryingthe desired gene

1 Cutting out the DNA of the desired gene

• The cell carrying the desired gene is broken

and its DNA is isolated from the other

components of the cell.

• An (3) enzyme works like a pair

of scissors to cut out the desired gene.

isolatedDNA

vector (e.g.a bacterial DNA)

desired gene vector cut-open

2 Inserting the gene into a vector

• The desired gene is put into a

(4) vector (��) which acts as a

carrier to carry the gene into a host cell.

• The gene is inserted into the vector with

the help of another enzyme which works

like glue. vector with desired gene]

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3 Introducing the vector into the host cell

• The host cell allows the vector to

(1) replicate .

• The host cell can be a bacterium, a yeast

cell or even a mammalian cell.

host DNA host cell

4 Multiplying copies of the gene

by the host cell

• As the host cell (2) divides ,

identical copies of the desired gene are also

produced in all the new cells.

•� The new cells are then able to synthesize

the new protein, e.g. human insulin.

Go To …Section concept diagram (Student’s Book 3 p.238)

Quick check (Student’s Book 3 p.238)�

24.2 How is genetic engineering applied? (Book 3, p.239)

• An organism of which genetic information has been changed in a way that does not occur

naturally by mating is called a (3) GMO (genetically modified organism ������).

•� It can be applied in (4) food production and the production of (5) human

insulin .

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1 Application in food production (Book 3, p.239)

• (1) GM food (genetically modified food ������) is food

which results from GM plants and animals.

Examples of GM food (Book 3, p.239)

• GM corn can produce a (2) toxin when

attacked by pests because a gene for this protein,

originally from a species of bacterium, is introduced.

• GM tomatoes can last longer because a gene

causing the (3) softening of tomatoes is

‘switched off’.

• GM rice can produce a substance which will be converted to

(4) vitamin A in humans because three genes from

other plants are introduced.

• Powdered milk from GM cows contains a (5) human

protein which is good for premature babies.

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♦�How to produce a GM corn plant which resists pests

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Implications of the use of GMO in food production (Book 3, p.241)

Potential benefits

1 Increased (1) crop yields

e.g. Scientists have developed GM potatoes with higher

annual yield than conventional potatoes.

2 Improved (2) nutritional value

e.g. GM rice containing more vitamin A and iron may

help solve some problems of malnutrition in the third

world.

3 Increased (3) resistance to pests, and increased

tolerance to cold, drought or high salinity of soil

e.g. GM corn can produce a toxin when attacked by pests,

thus reducing the use of pesticides.

4 Elimination of allergy-causing properties of food

e.g. The proteins in the milk from GM cows are modified

so that they will not cause allergies to certain people.

5 Improved (4) flavour and texture of food

e.g. The content of GM milk is modified to give a more

desirable flavour.

6 Reduction of (5) wastage and (6) cost

e.g. GM tomatoes can last longer and be sold in the

market for a longer time. Expiry dateMarch 06

Expiry dateJan 06

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Criticisms (Book 3, p.242)

1 Threats to human health

• GM food may cause unknown harmful effects to human (1) health .

•� GM food may lead to transfer of (2) antibiotic resistance genes to pathogens.

2 Threats to the environment

• Accidental release of GMOs into the environment may disturb (3) ecological

balance .

•� Accidental release of GMOs into the environment may cause genetic pollution.

3 Threats to third world farmers

• Production of GM food by industrialized countries poses a (4) financial

threat to the third world farmers.

Threats to human health?Threats to the environment?

Threats to third world farmers?

Ethical problems?

Possible production of ‘super organisms’?

GM food

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4 Ethical problems

• Production of GM food violates the (1) value of organisms in nature.

•� Some people may have eaten food which contains a gene from organisms which they should

not eat for religious, health or other reasons.

5 Possible production of ‘super organisms’

• Any ‘super organisms’ resulting from genetic engineering may (2) compete with the

natural organisms in the environment.

•� ‘Super humans’ may be produced, endangering the life of humans and other organisms.

♦ The production and the consumption of GM food have been controversial

Go To …STS connection 24.1 Issues related to genetically modified food and genetic engineering

(Student’s Book 3 p.244; Activity Book 3 p.127)�

E 2 Application in production of insulin (Book 3, p.244)

• In the past, animal insulin was injected into patients to

control diabetes. However, animal insulin was expensive and

slightly different from human insulin.

• With advances in genetic engineering, human insulin can be

produced by (1) E. coli , which is a GM bacteria.

♦ Injection of insulin

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insulin gene

human cellcarrying theinsulin gene

insulin gene

The insulin gene is isolated and insertedinto a vector.

The vector is introduced into an E. coli.

vector

As the E. coli divides, copies of the insulin geneare also produced and then large amounts ofinsulin are made by protein synthesis.

The insulin is extracted and purified forsale and use.

insulin

♦�Production of insulin by GM E. coli

Go To …STS connection 24.2 Application of genetic engineering in the pharmaceutical industry

(Student’s Book 3 p.246; Activity Book 3 p.129)

Quick check (Student’s Book 3 p.247)

Review (Student’s Book 3 p.247)

Summary concept diagram (Student’s Book 3 p.248)

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Practice question

The timeline below shows the development of genetic engineering.

a What is genetic engineering? (2 marks)

Genetic engineering refers to the laboratory techniques which enable biologists to change

the genetic information of an organism (1m). Using these techniques, genes can be

manipulated to increase the variation of species (1m).

b Describe how biologists may introduce viral resistance into the tobacco plants. (5 marks)

The gene for the viral resistance is isolated and inserted into a vector (1m). The vector

carrying the desired gene is introduced into a host cell (1m). The tobacco cells are

cultured with the host cells carrying the gene in a flask (1m). The vectors enter the

tobacco cells (1m). Eventually, the tobacco cells develop into viral resistant plants (1m).

c Apart from viral resistance, give one other example of desirable property that can be

introduced into crops. (1 mark)

Resistance to pests / higher yield / more nutritional. (1m)

d Give two examples of environmental issues associated with living GMOs. (2 marks)

Living GMOs may disturb the ecological balance in a habitat. / They may modify similar

plant species by cross-pollination. (1m x 2)

Total: 10 marks

� END �

1953Double helixstructure of DNAworked out

1986Growing of the first GMvirus-resistant tobaccoplants approved

1990Discussion on thesafety of GM foodstarted in WHO

1994First GM tomatoesput on market

2003- Safety assessment standards of GM food set up- Agreement addressing the environmental issues

associated with living GMOs became effective