Genetic Engineering

1. 1 Describe [2 marks]

   Describe what is meant by genetic engineering.

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   Model answer

   Genetic engineering is a process that changes the genome of an organism. A gene is inserted into the organism (often from another species) to give it a desirable characteristic.

   Mark scheme

   • Modifying the genome of an organism — 1 mark
   • By inserting a gene to give a desirable characteristic — 1 mark
2. 2 Describe [3 marks]

   The diagram shows how genetically engineered bacteria are used to make human insulin. Describe how the insulin is produced.

   

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   Model answer

   The human insulin gene is cut out of human DNA and inserted into a bacterium. The bacteria are grown in a fermenter, where they divide and make human insulin. The insulin is collected and purified so that it can be used by people with diabetes.

   Mark scheme

   • The human insulin gene is cut out and put into bacteria — 1 mark
   • The bacteria grow and make insulin in a fermenter — 1 mark
   • The insulin is collected and purified — 1 mark
3. 3 Give [2 marks]

   Give two differences between genetic engineering and selective breeding.

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   Model answer

   In genetic engineering a chosen gene is put directly into the genome, but in selective breeding the parents with the wanted characteristics are chosen and bred. Genetic engineering can use a gene from any species and can make the change in one step, whereas selective breeding needs many generations and can only use alleles that already exist in the species.

   Mark scheme

   • A gene is transferred directly, not through breeding — 1 mark
   • Can use genes from other species, or takes one step instead of many generations — 1 mark
4. 4 Explain [3 marks]

   A gene for resistance to a pest is inserted into a single cell from a maize plant. The cell is grown into a whole plant. Explain why every cell in the new plant has the gene.

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   Model answer

   The cell divides by mitosis to grow into the plant. Mitosis produces genetically identical cells, so the gene is copied each time. All the cells in the plant therefore contain the new gene.

   Mark scheme

   • The cell divides by mitosis — 1 mark
   • Mitosis makes genetically identical cells, or the DNA is copied — 1 mark
   • So every cell in the plant has the inserted gene — 1 mark
5. 5 Explain [4 marks]

   Maize can be genetically engineered to contain the Bt gene from a bacterium. Explain how this could increase the yield of the maize crop.

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   Model answer

   The Bt gene is cut out of the bacterium and inserted into the maize cells. The maize cells then make the protein that the gene codes for. This protein harms the caterpillars that eat the maize plants. So fewer plants are damaged by the pest, and more of the crop survives to be harvested, which increases the yield.

   Mark scheme

   • The gene is inserted into the maize cells — 1 mark
   • The maize makes the protein coded for by the gene — 1 mark
   • The protein kills or harms caterpillars that eat the plant — 1 mark
   • Less damage by pests, so a higher yield — 1 mark
6. 6 Explain [3 marks]

   Before 1982 insulin for people with diabetes was taken from the pancreases of pigs. Explain two advantages of using insulin made by genetically engineered bacteria instead.

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   Model answer

   The bacteria make human insulin, which is identical to the person's own, so it is less likely to cause a reaction than pig insulin. The bacteria reproduce quickly, so a very large amount of insulin can be made cheaply.

   Mark scheme

   • It is human insulin, identical to the person's own — 1 mark
   • So there is less risk of a reaction (or it works better) — 1 mark
   • A second advantage, such as large amounts made quickly and cheaply, or no animals used — 1 mark
7. 7 Describe [4 marks]

   Describe the main stages in producing a crop plant that is genetically engineered to resist an insect pest.

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   Model answer

   A gene that makes a protein that harms the pest is found in another organism, such as the Bt gene in a bacterium. The gene is cut out of the DNA of the donor using enzymes. It is inserted into the DNA of a plant cell. The cell is then grown into a whole plant, which makes the protein in all of its cells and can be tested to see whether it resists the pest.

   Mark scheme

   • Find a gene for pest resistance in another organism — 1 mark
   • Cut it out with enzymes — 1 mark
   • Insert it into plant cells — 1 mark
   • Grow the cells into plants (and test them) — 1 mark

Quick check

1. 1

   What is genetic engineering?

   1. ABreeding the best parents together
   2. BChanging the genome by inserting a gene
   3. CGrowing plants without soil
   4. DCopying an animal from one of its cells
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   B: Changing the genome by inserting a gene

   Genetic engineering modifies the genome of an organism, by inserting a gene, to give it a desirable characteristic.

2. 2

   Why can a gene from a bacterium be used in a maize plant?

   1. AMaize cells cannot make proteins
   2. BBacteria and maize are the same species
   3. CThe maize cells make the protein that the gene codes for
   4. DThe gene turns maize into a bacterium
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   C: The maize cells make the protein that the gene codes for

   The gene is put into the genome of the maize cells, which then make the protein that the gene codes for.

3. 3

   Why is a new gene usually inserted into a cell at an early stage?

   1. ASo that it is copied into every cell by mitosis
   2. BSo that the organism does not need to eat
   3. CSo that no enzymes are needed
   4. DSo that the gene changes its own code
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   A: So that it is copied into every cell by mitosis

   Mitosis copies the gene into every new cell, so that every cell in the adult organism has it.

4. 4

   What does the Bt gene do in maize?

   1. AIt makes the maize grow without water
   2. BIt gives the maize extra vitamin A
   3. CIt makes the maize resistant to weedkiller
   4. DIt makes the maize produce a protein that kills caterpillars
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   D: It makes the maize produce a protein that kills caterpillars

   The Bt gene makes the maize produce a protein that harms the caterpillars that feed on it.

5. 5

   Where are GM bacteria that make insulin grown?

   1. AIn a pig's pancreas
   2. BIn a fermenter
   3. CIn a field
   4. DIn a human cell
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   B: In a fermenter

   Large tanks called fermenters give the bacteria the conditions to grow and make insulin.

6. 6

   Which is an advantage of insulin made by GM bacteria, compared with insulin from pigs?

   1. AIt is made more slowly
   2. BIt is a different shape from human insulin
   3. CIt is identical to human insulin
   4. DIt is made from animals
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   C: It is identical to human insulin

   Bacteria make human insulin, which is identical to the person's own, so there is less chance of a reaction.

7. 7

   How is genetic engineering different from selective breeding?

   1. AA gene is moved directly, in one step
   2. BIt takes many generations
   3. CIt only uses genes from the same species
   4. DIt involves choosing the best parents
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   A: A gene is moved directly, in one step

   Genetic engineering moves a chosen gene in one step, while selective breeding takes many generations.

8. 8

   Which of these organisms is genetically modified?

   1. AA cow bred to give more milk
   2. BA wheat plant with a short stem
   3. CA dog bred for a calm temperament
   4. DA bacterium that makes human insulin
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   D: A bacterium that makes human insulin

   Bacteria with the human insulin gene have had their genome changed by genetic engineering.