Genetic engineering

The growth of crop plants, such as wheat, can be improved by the use of fertilisers and the control of pests.

Figure 13 shows the mass of grains produced by wheat plants grown in soil without fertiliser and in soil with fertiliser.

Give one effect on the grains produced, when wheat plants are grown in soil with fertiliser.

Explain why farmers measure the mass of 1000 grains rather than the mass of one wheat grain.

Biological control can be used to reduce pest damage on crops.

Which is the definition of biological control?

Figure 14 shows a crop being grown under a clear plastic cover and a crop being grown in a garden.

Explain why biological control would be more successful when a crop is grown under a clear plastic cover.

* (d) Figure 15 shows corn damaged by an insect pest.

Scientists have genetically modified (GM) corn plants to be

• resistant to insects

• resistant to weedkillers

Explain the advantages and disadvantages of growing GM corn plants.

State why the embryo of the pig must be engineered so it does not grow pig kidneys.

Explain why human stem cells are used for this process.

Figure 9 shows the number of organ transplants needed and the number of donors available in the USA from 1991 to 2018.

Compare the number of donors available with the number of organ transplants needed from 1991 to 2018.

Use information from the graph to support your answer.

State why scientists are genetically engineering animals for organ transplants.

*(c) Bacteria have been genetically engineered to produce human insulin since 1978.

Explain how bacteria can be genetically engineered to produce human insulin.

7 (a) Figure 14 shows the limbs of some animals.

Figure 14

Describe how these limbs provide evidence for evolution.

(b) Prickly pear cacti are weeds that grow in many countries. Insects have been used to limit the population of prickly pear cacti. Figure 15 shows some insects on a prickly pear cactus.

(Source: © Catherine Eckert/Shutterstock)

Figure 15

(i) Which is the name of this method of limiting the population of weeds?

(ii) Give two benefits of using insects, rather than chemicals, on prickly pear cacti.

* (c) Some crop plants have been genetically modified to be resistant to insect pests. Explain the advantages and disadvantages of producing genetically modified crop plants.

8 Chymosin is an enzyme that causes milk to curdle. When milk curdles the proteins in the milk clump together and become solid.

(a) As part of an investigation, milk was heated in test tubes to different temperatures using a Bunsen burner. Two drops of chymosin solution were added to each test tube and the time taken for the milk to curdle was recorded. Figure 11 shows the results.

Figure 11

(i) Which variables need to be kept constant in this investigation?

(ii) Explain why the time taken for the milk to curdle decreases from 30°C to 40°C.

(iii) Explain what the expected result would be if two drops of chymosin were added to the milk at 70°C in the test tube.

(iv) As part of this investigation, test tubes containing only milk were heated to each temperature and no chymosin solution was added. State why these test tubes containing only milk were used.

(v) Describe two improvements that could be made to the method of this investigation so that the optimum temperature for chymosin can be found.

(b) Chymosin can be produced by genetically modified bacteria. Figure 12 shows a bacterial cell.

Figure 12

Explain how to genetically modify a bacterial cell to produce chymosin.

Figure 5 shows the area of land used to grow genetically modified (GM) crops worldwide from 2005 to 2014.

In 2009, the area of land used was 134 million hectares and in 2010 the area of land was 147 million hectares.

Complete Figure 5 by drawing bars to show the area of land used in 2009 and 2010.

Describe the trend shown by the data in Figure 5.

GM crops often produce a larger yield than non-GM crops.

Give one reason why this could reduce the destruction of forests.

The ladybird is a predator.

Aphids are insect pests.

Figure 6 shows a ladybird feeding on aphids.

Figure 6

Using ladybirds to control insect pests is an example of

Explain one advantage of using predators to control insect pests.

Some crop plants are genetically modified to make them resistant to attack by insect pests.

State one disadvantage of genetically modified crop plants.

Bacteria grown in a liquid medium is called a bacterial culture. As the number of bacteria increases the bacterial culture becomes opaque. This is because light is absorbed by the bacterial culture.

To measure the increase in the number of bacteria, a scientist took a sample from the culture every 20 minutes.

The apparatus shown in Figure 7 detects the amount of light transmitted through the bacterial sample and uses it to calculate the amount of light absorbed.

Give two aseptic techniques the scientist should use when taking samples from the bacterial culture.

Figure 8 shows the amount of light absorbed by the bacterial sample.

The bacterial population increases rapidly between 40 and 100 minutes.

Calculate the time taken for the amount of light being absorbed by the bacterial sample to double from 0.5 to 1.0 arbitrary units.

The scientist put a small sample of the bacteria on a microscope slide and used a magnification of ×1000 to view the sample.

The bacteria could not be seen very clearly.

Give one improvement the scientist could make to view the bacteria more clearly.

Some bacteria contain a gene that produces a toxin that can kill insects.

This gene can be inserted into the genome of a crop plant.

What method is used to insert the gene from the bacteria into the crop plant?

*(ii) Discuss the advantages and disadvantages of growing crop plants that produce a toxin that can kill insects.

Figure 4 shows the structures in a leaf.

Explain how structure Z is involved in defence against pathogens.

Chemicals can be extracted from plants.

Some of these chemicals can kill bacteria.

A scientist spread some bacteria on a nutrient agar plate as shown in Figure 5.

What is being shown in Figure 5?

Explain why the scientist worked near to a Bunsen burner.

A scientist spread bacteria onto the surface of two agar plates.

A filter paper disc was placed in the centre of each plate.

Each filter paper disc had been soaked in a different chemical extracted from plants.

The results are shown in Figure 6.

The area of a circle is calculated using πr².

Calculate the area of the zone of inhibition for chemical A.

Use π = 3.14

The scientist concluded that chemical A was more effective than chemical B at killing bacteria.

Give two variables the scientist needed to control to make this conclusion valid.

Some crop plants have been genetically engineered to produce toxic chemicals in their leaves.

Explain one advantage of producing these genetically modified crop plants.

Organisms can be classified by the five kingdom or three domain method.

What is the name of the domain that plants belong to?

Plant cells contain chloroplasts.

What happens in a chloroplast?

Give a reason why the three domain method of classification has been suggested.

Figure 7 shows a cyanobacterium magnified 50 000 times.

The line AB shows the diameter of the bacterial cell.

(Source: © The Christian Science Monitor)

Figure 7

Calculate the actual diameter of the cyanobacterium.

Give your answer in micrometres (µ m).

Bacterial cells contain plasmids.

Describe three other features of a bacterial cell.

Figure 8 shows a plasmid containing the human insulin gene.

Explain how the human insulin gene can be inserted into a plasmid.

(a) Yeast cells can be genetically modified to produce a painkiller.

This painkiller is usually obtained from opium poppies.

One method for genetically modifying a yeast cell uses a plasmid containing the desired gene.

Explain how a gene can be inserted into a plasmid.

Discuss the possible benefits and risks of producing painkillers from genetically modified yeast cells rather than extracting the painkillers from poppies.

Figure 17 shows the structure of a DNA nucleotide.

Structure A is a

*(ii) In 2003, the first complete human genome was sequenced.

The genomes of different people have small changes in the sequence of the DNA bases.

Describe how these changes in DNA sequence can affect the individuals and how sequencing a person’s genome could influence their medical treatments.