Exam questions · Biology
Selective Breeding and Genetic Engineering
- 42 exam questions
- 149 marks
- 63 quick checks
Selective Breeding
Just this lesson-
1 State [2 marks]
State two characteristics that have been selected by selective breeding in food crops.
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Model answer
Any two from: disease resistance, large fruit or grain, high yield, better taste.
Mark scheme
- First characteristic — 1 mark
- Second characteristic — 1 mark
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2 Describe [4 marks]
Describe how selective breeding could be used to produce a variety of wheat with a high yield.
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Model answer
Choose wheat plants that have a high yield. Breed them together. From the offspring, select the plants with the highest yield, and breed from those. Repeat the process for many generations, until the wheat reliably gives a high yield.
Mark scheme
- Choose high-yield plants — 1 mark
- Breed them together — 1 mark
- Select the best offspring — 1 mark
- Repeat over many generations — 1 mark
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3 Calculate [3 marks]
The wheat yield of a field increased from 4.0 tonnes per hectare to 7.8 tonnes per hectare after 40 years of selective breeding. Calculate the percentage increase.
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Model answer
The increase is 7.8 − 4.0 = 3.8. The percentage increase is 3.8 ÷ 4.0 × 100 = 95%.
Mark scheme
- Increase of 3.8 — 1 mark
- Divide by 4.0 and multiply by 100 — 1 mark
- 95% — 1 mark
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4 Explain [3 marks]
Explain why inbreeding in a breed of dog can lead to genetic disorders.
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Model answer
Inbreeding means breeding between close relatives, which are likely to carry the same alleles. This makes it more likely that two copies of a harmful recessive allele will be inherited by the offspring. The offspring then show the genetic disorder.
Mark scheme
- Close relatives carry the same alleles — 1 mark
- Two copies of a harmful recessive allele more likely — 1 mark
- So offspring show the disorder — 1 mark
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5 Explain [4 marks]
Explain how selective breeding reduces the genetic variation in a population, and why this could be a problem.
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Model answer
In selective breeding only a few individuals with the desired characteristic are chosen to breed, so only some of the alleles are passed on and others are lost. The population becomes genetically similar. This is a problem because a new disease or a change in the environment could affect all of the individuals, as none has a different allele that could give resistance.
Mark scheme
- Only a few individuals breed — 1 mark
- Some alleles lost — 1 mark
- Population genetically similar — 1 mark
- A disease could affect all — 1 mark
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6 Evaluate [6 marks]
Evaluate the use of selective breeding to increase the milk yield of dairy cattle.
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Model answer
Selective breeding has greatly increased the milk yield per cow, which means more milk is produced from fewer cows, and this helps to feed more people and can lower costs for farmers. However, the cows are bred from a small number of bulls, so the genetic variation is low, and a disease could affect the whole herd. Cows with very high yields can also suffer health problems such as mastitis and lameness, which is a welfare issue. It also takes many generations to achieve. Overall, selective breeding is useful, but the health and welfare of the animals must be considered, as well as the yield.
Mark scheme
- Higher yield / more food — 1 mark
- Lower costs or fewer cows — 1 mark
- Reduced variation, disease risk — 1 mark
- Welfare / health problems — 1 mark
- Slow — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
What is selective breeding?
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B: Humans choosing which organisms to breed
In selective breeding, humans choose which organisms breed so that desired characteristics become more common.
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2
Which is the first step in selective breeding?
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A: Choose parents with the desired feature
The first step is to choose parents that have the desired characteristic.
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3
Why is selective breeding repeated for many generations?
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D: To make the desired feature gradually stronger
The characteristic gradually becomes stronger and more common with each generation.
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4
Which is a drawback of selective breeding?
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C: It reduces genetic variation
Breeding from a few individuals reduces genetic variation.
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5
Which of these came from selective breeding of wild cabbage?
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B: Broccoli
Broccoli, kale and cauliflower all came from the wild cabbage by selective breeding.
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6
What is inbreeding?
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A: Breeding between close relatives
Inbreeding is breeding between close relatives.
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7
A herd's milk yield rose from 4000 to 6000 litres per cow. What is the percentage increase?
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C: 50%
The increase is 2000, and \(2000 \div 4000 \times 100 = 50\%\).
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8
How does artificial selection differ from natural selection?
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D: People choose which individuals breed
In artificial selection, people choose which individuals breed.
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9
A farmer breeds only the sheep with the thickest wool for many years. What is likely to happen to the genetic variation of the flock?
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B: It decreases
Only some alleles are passed on, so the variation in the flock decreases.
Tissue Culture
Just this lesson-
1 State [2 marks]
State two conditions that must be provided for explants to grow in tissue culture.
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Model answer
Any two from: sterile conditions, nutrients, plant hormones, warmth, light.
Mark scheme
- First condition — 1 mark
- Second condition — 1 mark
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2 Name [2 marks]
Name the mass of undifferentiated cells that forms in tissue culture, and the small plants that grow from it.
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Model answer
A callus, and plantlets.
Mark scheme
- Callus — 1 mark
- Plantlets — 1 mark
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3 Explain [3 marks]
Explain why all of the tools and equipment used in tissue culture must be sterile.
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Model answer
Microorganisms such as bacteria and fungi grow much faster than plant cells. If they got into the culture they would compete with the plant cells for nutrients and might kill them or spoil the culture.
Mark scheme
- Microorganisms grow faster — 1 mark
- They compete for nutrients — 1 mark
- Could kill the cells / spoil the culture — 1 mark
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4 Calculate [3 marks]
A grower takes 40 explants from a rare orchid. Each explant produces a callus that makes 25 plantlets. Calculate the total number of plantlets, and state the genetic relationship between them.
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Model answer
40 × 25 = 1000 plantlets. They are genetically identical clones of the parent orchid.
Mark scheme
- 40 × 25 — 1 mark
- 1000 plantlets — 1 mark
- Clones, genetically identical — 1 mark
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5 Explain [4 marks]
Explain two advantages of using tissue culture in a plant breeding programme.
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Model answer
It can produce a large number of identical plants quickly, so a plant with a useful characteristic, such as disease resistance, can be copied in large numbers. It can also produce plants that are free of disease, because the cells from the shoot tip may not contain viruses, so the plants are healthier and give a better yield.
Mark scheme
- Many plants quickly — 1 mark
- Developed: copy useful feature — 1 mark
- Disease-free plants — 1 mark
- Developed: viruses not in tip — 1 mark
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6 Evaluate [6 marks]
Evaluate the use of tissue culture to produce plants and for medical research.
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Model answer
In plant breeding, tissue culture produces large numbers of identical plants quickly, all year round, in a small space, and the plants can be disease-free. It can save rare species. In medical research cultured cells can be used to test drugs and study diseases such as cancer, which reduces the use of animals. However, it is expensive and needs a sterile technique and skilled workers, and contamination can ruin the cultures. The plants are clones, so there is no variation, and a disease could harm all of them. Overall it is very useful when it is used carefully, but it should be combined with other methods to keep genetic variation.
Mark scheme
- Many identical plants quickly — 1 mark
- Disease-free / saves rare species — 1 mark
- Medical research use — 1 mark
- Expensive, skilled workers, contamination — 1 mark
- Clones, no variation — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
What is a callus?
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C: A mass of undifferentiated cells
A callus is a mass of undifferentiated plant cells that grows in tissue culture.
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2
Why is the agar used in tissue culture sterile?
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B: To stop microorganisms growing
Sterile agar stops microorganisms growing and competing with the plant cells.
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3
What is added to the agar to make plant tissue grow?
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A: Nutrients and plant hormones
The agar contains nutrients and plant hormones, which make the cells grow and differentiate.
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4
Which describes plants made by tissue culture?
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D: They are genetically identical clones
They all come from one parent by mitosis, so they are genetically identical clones.
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5
Which is an advantage of tissue culture?
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C: It makes many identical plants quickly
Many identical plants can be produced quickly, all year round.
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6
Which is a disadvantage of tissue culture?
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A: The plants have no genetic variation
The plants are clones with no variation, so a disease could affect all of them.
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7
Why can tissue culture be used to make disease-free plants?
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B: Shoot tip cells are often virus-free
Cells in the tip of the shoot are often free from viruses, so the plants grown from them are disease-free.
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8
How can cultured human cells help to develop a new cancer drug?
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D: By allowing the drug to be tested on cells
The drug can be tested on the cells in a dish, without using a person or animal.
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9
A grower wants to keep a rare orchid from extinction. Why is tissue culture useful?
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A: Many plants can be grown from a small piece of tissue
A small piece of tissue can be made into hundreds of plants, without taking plants from the wild.
Genetic Engineering
Just this lesson-
1 State [2 marks]
State what is meant by genetic engineering.
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Model answer
Modifying the genome of an organism by introducing a gene from another organism, to give a desirable characteristic.
Mark scheme
- Modifying the genome — 1 mark
- Introducing a gene from another organism — 1 mark
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2 State [2 marks]
State two uses of genetic engineering.
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Model answer
Any two from: making human insulin in bacteria, making insect-resistant crops, making golden rice, gene therapy, making other human proteins.
Mark scheme
- First use — 1 mark
- Second use — 1 mark
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3 Explain [3 marks]
Explain why bacteria can be genetically engineered to make human insulin.
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Model answer
All living things use the same genetic code, so a bacterium reads the base sequence of the human insulin gene in the same way as a human cell. The bacterium therefore makes the same amino acid sequence, and the protein folds to produce human insulin.
Mark scheme
- Same genetic code — 1 mark
- Bacteria can transcribe and translate the gene — 1 mark
- Makes the same protein — 1 mark
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4 Describe [4 marks]
Describe how a gene from one organism can be put into a bacterium, to make a new protein.
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Model answer
The gene is found and removed from the DNA of the organism. It is inserted into a vector, such as a plasmid, which is put into a bacterium. The bacteria are grown in a fermenter, and each time they divide they copy the gene. The bacteria make the protein.
Mark scheme
- Gene removed — 1 mark
- Inserted into a vector / plasmid — 1 mark
- Vector put into the bacteria — 1 mark
- Bacteria grown and make the protein — 1 mark
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5 Compare [4 marks]
Compare genetic engineering with selective breeding.
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Model answer
Selective breeding uses the genes already in a species, whereas genetic engineering can use a gene from any species. Selective breeding takes many generations, but genetic engineering can produce a change in one generation. In selective breeding whole organisms are chosen, but in genetic engineering a single gene is moved. Genetic engineering can therefore give completely new characteristics.
Mark scheme
- Genes already in the species / any species — 1 mark
- Many generations / one generation — 1 mark
- Whole organisms / single gene — 1 mark
- New characteristics — 1 mark
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6 Evaluate [6 marks]
Evaluate the use of genetic engineering to produce human insulin, compared with extracting insulin from animals.
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Model answer
Insulin made by genetically engineered bacteria is identical to human insulin, so there is less chance of an allergic reaction, and it does not depend on animal pancreases, so large amounts can be made at lower cost. Bacteria grow quickly in fermenters, so the supply is reliable. It also avoids the ethical issues of using animals. However, setting up the process is expensive, and some people are concerned about the safety of genetic engineering, although there is no evidence of harm. Overall it is a major success because it is safe, reliable and gives a large supply of pure insulin.
Mark scheme
- Identical to human insulin — 1 mark
- Large, reliable supply — 1 mark
- Fewer animal ethical issues — 1 mark
- Cost to set up / concerns — 1 mark
- No evidence of harm — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
What is a genetically modified organism?
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B: An organism with a gene added by genetic engineering
A GM organism has had its genes changed by genetic engineering.
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2
Why can a human gene work in a bacterium?
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A: All organisms use the same genetic code
All living things use the same genetic code.
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3
Which product is made by genetically engineered bacteria?
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C: Human insulin
Bacteria with the human insulin gene make human insulin.
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4
What is a plasmid?
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D: A small ring of DNA
A plasmid is a small ring of DNA in a bacterium.
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5
When was GM human insulin first approved for use?
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B: 1982
The first GM insulin was approved in 1982.
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6
What is golden rice?
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A: Rice that makes beta-carotene
Golden rice is GM rice that makes beta-carotene, which the body can turn into vitamin A.
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7
Which is an advantage of genetic engineering over selective breeding?
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C: It can add genes from any species
Genetic engineering can add a gene from any species, and the change happens in one generation.
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8
What is a vector in genetic engineering?
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D: A carrier that moves a gene into a cell
A vector, such as a plasmid, carries a gene into a cell.
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9
Why do all the descendants of a GM bacterium also make the human protein?
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B: The gene is copied each time the cell divides
The gene is copied with the rest of the DNA every time the bacterium divides.
The Stages of Genetic Engineering (Higher tier)
Just this lesson-
1 State [2 marks]
State the functions of (a) a restriction enzyme and (b) DNA ligase in genetic engineering.
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Model answer
(a) It cuts DNA at a specific base sequence. (b) It joins pieces of DNA together.
Mark scheme
- Restriction enzyme cuts — 1 mark
- Ligase joins — 1 mark
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2 Explain [3 marks]
Explain why the same restriction enzyme is used to cut the gene and the plasmid.
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Model answer
The enzyme cuts both at the same specific base sequence, and leaves sticky ends. The sticky ends on the gene and on the plasmid are therefore complementary, so they can pair up with each other.
Mark scheme
- Cuts at the same base sequence — 1 mark
- Leaves sticky ends — 1 mark
- Sticky ends are complementary, and pair up — 1 mark
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3 Describe [3 marks]
Describe what is meant by a vector in genetic engineering, and give an example.
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Model answer
A vector is a carrier that is used to transfer a gene into a host cell. An example is a plasmid, which is a small ring of DNA from a bacterium.
Mark scheme
- A carrier / transfers a gene — 1 mark
- Into a host cell — 1 mark
- Plasmid (or virus) — 1 mark
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4 Complete [2 marks]
A restriction enzyme leaves a sticky end with the bases G G C C. Write the bases of the complementary sticky end.
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Model answer
C C G G.
Mark scheme
- G pairs with C, and C pairs with G — 1 mark
- C C G G — 1 mark
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5 Explain [4 marks]
Explain how a gene can be inserted into a plasmid.
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Model answer
The plasmid is cut open using a restriction enzyme, which leaves sticky ends. The gene is cut out with the same enzyme, so it has complementary sticky ends. When they are mixed, the sticky ends pair up. DNA ligase then joins the gene into the plasmid, to make recombinant DNA.
Mark scheme
- Plasmid cut with a restriction enzyme — 1 mark
- Gene cut with the same enzyme, giving complementary sticky ends — 1 mark
- Sticky ends pair up — 1 mark
- DNA ligase joins them — 1 mark
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6 Describe [6 marks]
Describe the main stages in the production of human insulin by genetically engineered bacteria.
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Model answer
A restriction enzyme is used to cut the human insulin gene from human DNA, leaving sticky ends. The same enzyme is used to cut open a bacterial plasmid, which is the vector, giving it matching sticky ends. The gene and the plasmid are mixed, so that the sticky ends pair up, and DNA ligase joins them together to make a recombinant plasmid. The plasmid is put into bacteria. The bacteria are grown in a fermenter, and they copy the plasmid and make human insulin. The insulin is then collected and purified.
Mark scheme
- Restriction enzyme cuts out the gene — 1 mark
- Same enzyme cuts the plasmid / sticky ends — 1 mark
- Sticky ends pair up — 1 mark
- DNA ligase joins — 1 mark
- Plasmid put into bacteria — 1 mark
- Grown in a fermenter and the insulin purified — 1 mark
Quick check
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1
Which enzyme cuts DNA at a specific base sequence?
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A: Restriction enzyme
A restriction enzyme cuts DNA at a particular sequence of bases.
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2
Which enzyme joins pieces of DNA together?
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C: DNA ligase
DNA ligase joins DNA fragments, forming bonds in the backbone.
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3
What are sticky ends?
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B: Unpaired bases at the cut ends of DNA
They are short stretches of unpaired bases at the ends of DNA that has been cut by a restriction enzyme.
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4
Why do the sticky ends of the gene and of the plasmid match?
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D: The same restriction enzyme was used on both
The same enzyme cut both, so the unpaired bases are complementary.
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5
Which is used as a vector?
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A: A plasmid
A plasmid is a small ring of DNA that is used to carry genes into bacteria.
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6
What is recombinant DNA?
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B: DNA from two different sources joined together
Recombinant DNA is DNA that has been made by joining DNA from two different sources.
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7
What is the sticky end that pairs with A T T C?
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C: T A A G
A pairs with T, T with A and C with G, so the complementary sequence is T A A G.
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8
Why are bacteria often used as host cells?
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D: They reproduce quickly
Bacteria grow and reproduce very quickly, so they can make a lot of the product.
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9
Why is a marker gene, such as one for antibiotic resistance, included in the plasmid?
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A: To show which bacteria have taken up the plasmid
Only a few bacteria take up the plasmid, and the marker shows which ones have, since only they survive the antibiotic.
GM Crops
Just this lesson-
1 Name [2 marks]
Name the bacterium that is the source of the gene for insect resistance, and name the substance that the gene codes for.
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Model answer
Bacillus thuringiensis. The gene codes for a toxin (a protein) that kills insects.
Mark scheme
- Bacillus thuringiensis — 1 mark
- A toxin / protein — 1 mark
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2 Explain [3 marks]
Explain how a crop containing the Bt gene is protected from insect pests.
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Model answer
The gene from Bacillus thuringiensis is in every cell of the crop plant, so the plant makes the Bt toxin. When a caterpillar eats the leaves, it takes in the toxin, and this kills it, so the crop is not damaged.
Mark scheme
- Plant has the Bt gene — 1 mark
- Plant makes the toxin — 1 mark
- Insects that eat it are killed — 1 mark
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3 Calculate [3 marks]
The yield of a conventional cotton field is 1.8 tonnes per hectare, and the yield of a Bt cotton field is 2.4 tonnes per hectare. Calculate the percentage increase in yield.
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Model answer
The increase is 2.4 − 1.8 = 0.6. The percentage increase is 0.6 ÷ 1.8 × 100 = 33%.
Mark scheme
- Increase of 0.6 — 1 mark
- Divides by 1.8, times 100 — 1 mark
- 33% — 1 mark
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4 Explain [4 marks]
Explain two advantages to a farmer of growing a GM crop that contains the Bt gene.
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Model answer
The crop is protected from insect pests, so less is lost and the yield is higher, and so the farmer makes more money. The farmer also does not need to spray as much insecticide, which saves money and time and reduces the chance of poisoning, and also reduces harm to other insects.
Mark scheme
- Higher yield — 1 mark
- Developed — 1 mark
- Less insecticide — 1 mark
- Developed — 1 mark
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5 Explain [4 marks]
Explain how insects could become resistant to a Bt crop.
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Model answer
Some insects have a mutation that makes them less affected by the toxin. When the crop is grown, only these insects survive and reproduce, and they pass the allele on to their offspring. Over generations, more of the insects are resistant, so the crop no longer protects itself.
Mark scheme
- Mutation gives some resistant insects — 1 mark
- Only resistant insects survive — 1 mark
- They reproduce and pass on the allele — 1 mark
- The proportion of resistant insects increases — 1 mark
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6 Evaluate [6 marks]
Some people are in favour of GM crops and others are against them. Evaluate the advantages and the disadvantages of growing GM crops.
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Model answer
GM crops can have higher yields and need less insecticide, which saves farmers money, reduces pollution and can help to feed a growing population. Crops such as golden rice can also give important nutrients. However, there are concerns. Insect pests may evolve resistance to the toxin, so that the benefit is lost. The toxin or the modified genes might harm other organisms or spread to wild plants, which could reduce biodiversity. The seed is expensive and patented, which may be a problem for poor farmers, and some people worry about the safety of GM food, though no harm has been shown. Overall the benefits seem to be large, but the crops should be tested carefully and used with controls such as refuges.
Mark scheme
- Higher yield — 1 mark
- Less insecticide / less pollution — 1 mark
- Resistance may evolve — 1 mark
- Harm to other species / gene transfer — 1 mark
- Cost / patents / safety concerns — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
Which bacterium is used as the source of the Bt gene?
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C: Bacillus thuringiensis
The gene comes from Bacillus thuringiensis.
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2
What does the Bt gene make?
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A: A toxin that kills certain insects
The Bt gene codes for a toxin that kills certain insects.
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3
How does a Bt crop protect itself?
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D: It makes its own insecticide
The plant makes the toxin itself, so insects that eat it are killed.
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4
Which is an advantage of Bt crops?
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B: They need less insecticide
Farmers need to spray less insecticide.
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5
Why might insect pests become resistant to a Bt crop?
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A: Natural selection of insects that survive the toxin
Natural selection favours the insects that survive the toxin.
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6
What is the purpose of a refuge of non-GM crop?
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C: To keep non-resistant insects alive
It keeps some non-resistant insects, which slows down the evolution of resistance.
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7
A farmer sprays a field 5 times, and a Bt field once. What is the percentage reduction in spraying?
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D: 80%
The reduction is 4 out of 5, and \(4 \div 5 \times 100 = 80\%\).
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8
Which is a concern about GM crops?
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B: Genes could spread to wild plants
Genes could spread by pollen to wild plants, or the toxin could harm other insects.
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9
Golden rice was developed to help to prevent which problem?
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A: Vitamin A deficiency
Golden rice makes beta-carotene, which can be converted to vitamin A, and so helps to prevent vitamin A deficiency.
Feeding a Growing Population
Just this lesson-
1 State [2 marks]
State two minerals that plants need and one function of each.
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Model answer
Nitrate is needed to make proteins, and phosphate is needed to make DNA or for root growth. Potassium is needed for enzymes.
Mark scheme
- A mineral — 1 mark
- A correct function — 1 mark
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2 Define [2 marks]
Define the term biological control, and give one example.
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Model answer
Biological control is using a living organism to control a pest. An example is the use of ladybirds to eat aphids.
Mark scheme
- Using a living organism to control a pest — 1 mark
- An example — 1 mark
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3 Calculate [3 marks]
A farmer adds 100 kg of fertiliser to a field. The yield of potatoes increases from 20 tonnes to 32 tonnes. Calculate the percentage increase in yield.
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Model answer
The increase is 12 tonnes. The percentage increase is 12 ÷ 20 × 100 = 60%.
Mark scheme
- Increase of 12 — 1 mark
- Divides by 20, times 100 — 1 mark
- 60% — 1 mark
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4 Explain [4 marks]
Explain how fertiliser running off a field can lead to the death of fish in a nearby river.
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Model answer
The nitrates and phosphates in the fertiliser cause algae in the water to grow rapidly. The algae block out the light, so the plants under them die. Bacteria then break down the dead material and use up the oxygen in the water, so fish die from a lack of oxygen.
Mark scheme
- Nitrates / phosphates cause algal growth — 1 mark
- Light blocked, plants die — 1 mark
- Bacteria decompose them and use up oxygen — 1 mark
- Fish die from lack of oxygen — 1 mark
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5 Describe [3 marks]
The graph shows that the yield of wheat levels off at high levels of fertiliser. Describe the pattern and suggest why a farmer might not apply more than 200 kg per hectare.
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Model answer
The yield increases quickly at first, and then levels off, with very little extra above about 200 kg per hectare. Adding more fertiliser would be a waste of money, and could cause pollution, because the yield does not increase.
Mark scheme
- Rises then levels off — 1 mark
- Little extra yield above 200 kg — 1 mark
- Waste of money / pollution — 1 mark
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6 Evaluate [6 marks]
A farmer wants to protect a crop from aphids. Evaluate the use of ladybirds (biological control) compared with the use of a chemical pesticide.
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Model answer
Ladybirds feed on aphids but do not harm the crop, they do not leave chemicals in the food or water, and they will breed and may keep the pest down over a long time. A pesticide acts quickly and kills most of the aphids, but it may kill useful insects such as bees, can pollute the environment, and the aphids can evolve resistance. However, ladybirds work slowly and will not remove all of the aphids, and they may fly away. Overall, biological control is better for the environment and over the long term, but the farmer may need to use both, with the pesticide only when it is really necessary.
Mark scheme
- Ladybirds: no chemicals, specific — 1 mark
- Ladybirds: may breed and last — 1 mark
- Pesticide: fast and effective — 1 mark
- Pesticide: harms other insects, pollutes, resistance — 1 mark
- Ladybirds slow, not complete — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
What do plants use nitrates for?
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B: To make proteins
Nitrates are used to make proteins and chlorophyll.
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2
What is eutrophication?
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C: Algal growth caused by excess nutrients
Too many nutrients cause algae to grow rapidly, which leads to a lack of oxygen and the death of aquatic life.
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3
Which is a disadvantage of fertilisers?
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A: They can run off and cause eutrophication
Run-off causes eutrophication in rivers and lakes.
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4
Which is an example of biological control?
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D: Releasing ladybirds to eat aphids
Ladybirds are predators of aphids.
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5
Which is an advantage of biological control?
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B: It does not leave chemical residues
It does not leave chemicals in the food or the environment.
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6
What happened with cane toads in Australia?
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C: They became an invasive species
They did not control the cane beetles, and became an invasive pest.
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7
What does NPK stand for?
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A: Nitrogen, phosphorus, potassium
NPK is nitrogen, phosphorus and potassium.
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8
A yield rises from 4 to 6 tonnes after adding fertiliser. What is the percentage increase?
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D: 50%
The increase is 2, and \(2 \div 4 \times 100 = 50\%\).
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9
Why does the yield stop rising at high fertiliser levels?
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B: Another factor becomes limiting
Other factors, such as water or light, become limiting, so extra fertiliser has no further effect.
Evaluating Genetic Engineering and Selective Breeding
Just this lesson-
1 State [2 marks]
State two benefits of genetic engineering in medicine.
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Model answer
Any two from: it makes cheap, safe medicines such as insulin in large amounts; gene therapy can treat inherited disorders; it makes products such as growth hormone.
Mark scheme
- First benefit — 1 mark
- Second benefit — 1 mark
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2 State [2 marks]
State one practical issue and one ethical issue with genetic engineering.
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Model answer
A practical issue is that pests may become resistant or genes may spread to wild plants. An ethical issue is that some people think it is wrong to interfere with the genes of living things, or concern about patents.
Mark scheme
- Practical issue — 1 mark
- Ethical issue — 1 mark
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3 Compare [4 marks]
Compare genetic engineering and selective breeding in agriculture.
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Model answer
Selective breeding uses the genes that are already in the species and takes many generations, whereas genetic engineering can add a gene from any species in one generation. Selective breeding is cheaper, and genetic engineering is more expensive. Selective breeding can cause inbreeding and reduced variation, and genetic engineering raises concerns about safety and the environment.
Mark scheme
- Genes: same species / any species — 1 mark
- Many generations / one generation — 1 mark
- Cheaper / more expensive — 1 mark
- A different concern for each — 1 mark
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4 Explain [4 marks]
Explain why some people object to the use of genetic engineering in agriculture.
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Model answer
Some people think that it is wrong to interfere with the genes of living things. There are also worries that modified genes could spread to wild plants and harm other organisms, and that the long-term effects on health are unknown. Some are concerned that large companies own the seed, so that farmers become dependent on them.
Mark scheme
- Interfering with genes is wrong — 1 mark
- Genes could spread to wild plants — 1 mark
- Long-term effects not known — 1 mark
- Patents and control by companies — 1 mark
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5 Evaluate [6 marks]
Evaluate the use of genetic engineering to produce golden rice, which makes beta-carotene.
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Model answer
Golden rice makes beta-carotene, which the body can change into vitamin A, so it could prevent the blindness and deaths caused by vitamin A deficiency, especially in children in countries where rice is the main food. It could be grown by poor farmers if the seed is free. However, some people are concerned about the safety of GM food and the effect of the gene on the environment, and about the control of the seed by companies. Others say that it would be better to improve diets in other ways. The scientific evidence so far has shown no harm, so on balance the benefits seem to outweigh the risks, as long as it is tested and regulated properly.
Mark scheme
- Prevents vitamin A deficiency — 1 mark
- Helps poor people / main food — 1 mark
- Concern about safety or environment — 1 mark
- Concern about control by companies / alternatives — 1 mark
- No evidence of harm — 1 mark
- A reasoned conclusion — 1 mark
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6 Evaluate [6 marks]
A farmer is deciding whether to buy GM seed or to use conventional seed from selective breeding. Evaluate the two options.
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Model answer
GM seed may give a higher yield, because it resists pests, and it may reduce the cost of spraying, which would increase the farmer's profit and help the environment. But the seed is more expensive, and has to be bought new each year, and pests may become resistant. Conventional seed from selective breeding is cheaper and the farmer can save seed, and there is little public concern. However, the yield may be lower, and the crop may need more pesticide, and the plants may be less resistant. The best choice depends on the cost, the amount of pest damage and the market, but a mix of options may reduce risk.
Mark scheme
- GM: higher yield / less spraying — 1 mark
- GM: cost of seed / resistance — 1 mark
- Conventional: cheaper, save seed — 1 mark
- Conventional: lower yield, more pesticide — 1 mark
- Environmental point — 1 mark
- A reasoned conclusion — 1 mark
Quick check
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1
What should an evaluation include?
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C: Benefits, risks and a conclusion
An evaluation weighs up benefits and drawbacks, and ends with a justified conclusion.
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2
Which is a benefit of genetic engineering in medicine?
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A: Cheap, safe insulin in large amounts
GM bacteria can make large amounts of cheap, safe insulin.
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3
Which is an ethical issue about genetic engineering?
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D: Whether it is right to interfere with genes
Some people think that it is wrong to change the genes of living things.
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4
Which is a risk of selective breeding?
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B: It can cause inbreeding and reduced variation
Inbreeding can cause genetic disorders, and reduced variation makes populations vulnerable.
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5
Which method can move a gene from one species to another?
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A: Genetic engineering
Only genetic engineering can add a gene from a different species.
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6
Which is a concern about patents on GM seed?
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C: Farmers may depend on the companies for seed
Farmers may depend on a company, and have to buy new seed each year.
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7
Why is selective breeding usually less controversial than genetic engineering?
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D: It uses natural variation within a species
It uses the natural variation in a species, and does not move genes between species.
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8
Which statement is a good conclusion to an evaluation?
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B: On balance the benefits outweigh the risks because yields are higher, as long as there is regulation
A conclusion states a judgement and gives a reason for it, based on the evidence.
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9
A new GM crop increases yield by 20% but may harm wild plants. How should a scientist decide whether to approve it?
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A: Weigh the benefits and risks using evidence and testing
Decisions should weigh the evidence of benefits against the possible risks, test the crop carefully, and consider ethical views.