4.2 Genetic Modification

Fertilisers are widely used by farmers when growing crops for human and animal consumption. Many such fertilisers have to be applied every year to maintain the required quality of crop production. 

Explain why fertilisers are required on farmland whereas they are not required for land which is very plant-rich such as mature woodland. 

Figure 1 contains a list of mineral ions commonly added to artificial fertilisers.

Place a tick (✓) in Figure 1 against the three most commonly-used ions added to fertilisers.

Figure 1

The usage of nitrogen-containing fertiliser in an Eastern European country rose from 179 000 tonnes in 2009 to 359 000 tonnes in 2021.

Figure 1 shows a method of producing plants.
Step 1. Cells taken from parent plant.
Step 2. Cells placed on agar growth medium.
Step 3. Cells develop into tiny plantlets.
Step 4. Plantlets grown in compost.

Figure 1

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Genetically modified (GM) crops have been on the market since the 1990s. This biotechnology involves changing the DNA of one organism, often by inserting genes from another.

GM maize makes up more than 87% of all maize grown in the United States. The maize has been modified to contain the pesticide Bt, making it toxic to insects that try to eat it. The gene that makes Bt comes from the bacterium Bacillus thuringiensis, which produces a toxin that kills insects. 

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Figure 1 shows the number of Bt crops and the number of resistant species in an 80 hectare farm in the United States.

Figure 1

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Discuss why some people might disagree with the production of genetically modified crops.

Recent studies have shown that cancerous tumours can be targeted using genetically engineered bacteria. Research has shown that where chemotherapy and radiotherapy have been unsuccessful in treating cancerous tumours, the answer may lie with the use of bacteria as a therapeutic agent.

A group of bacteria, called Clostridium, can be modified with a gene that causes the bacteria to produce proteins which have been shown to destroy tumours.

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Selective breeding is another method used by humans so that organisms have desirable characteristics, such as selectively breeding cows to produce large volumes of high-quality beef.

The graph in Figure 1 shows information about the mass of beef produced by cattle in Ireland from 2012 to 2022. 

Figure 1

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Some people believe that selective breeding can cause issues with inbreeding. 

The pug is an ancient breed of dog which, in recent years, has suffered from issues caused by inbreeding. 

Figure 2 shows data collected about heart failure in pugs over a 12 month period in Boston, USA.

Figure 2

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Evaluate the benefits and risks of genetic engineering and selective breeding in modern agriculture.

You should include the practical and ethical implications in your answer.

Give three reasons why a farmer may wish to grow genetically modified (GM) crops.

Figure 1 shows a selectively-bred bull from the variety of beef cattle known as the Belgian blue.

Figure 1

Use your knowledge of selective breeding to suggest two benefits and two drawbacks of breeding from the bull shown in Figure 1. 

The owner of the bull shown in Figure 1 is able to extract the bull's semen and sell that to other cattle breeders to allow their cows to become pregnant with this bull's offspring. This practice is called artificial insemination (AI). 

State one advantage of farmers using AI during selective breeding. 

Tissue culture has also been used successfully to grow human cells in the laboratory. Specific tumour cells that lead to cancer can also be cultured. 

Suggest and explain a benefit to cancer research of growing such cells in the laboratory. 

Higher Tier only

Explain the meaning of the term 'vector' when used in genetic engineering. 

Higher Tier only

The table in Figure 5 sets out a number of steps in the production of human insulin in a process involving genetically-engineered bacteria. 

The statements are in the wrong order. 

Figure 5

Complete the table in Figure 6 to list the steps in the correct sequence.

The first step has been completed for you. 

Figure 6

In the 1970s, the major US agrochemical business Monsanto developed a family of chemical herbicides that it sold under the trade name Roundup™. 

Roundup™ is active against a very wide range of plants.

Monsanto also developed a range of genetically-modified crop seeds that were resistant to Roundup™.

Discuss the benefits and drawbacks of a farmer in the 1980s sowing seeds that were genetically modified to be resistant to Roundup™.

Higher tier content only

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.

The human population is increasing, so more food needs to be produced.

Farmers use fertilisers to increase the yield of wheat.

A farmer wants to find out the optimum concentration of fertiliser to use on his wheat plants.

He has a stock solution of concentrated fertiliser which is stated as 100%.
He dilutes the stock solution to make 5%, 10%, 15% and 20% solutions.

He makes 100 cm³ of each solution.

Figure 1 shows two varieties of potato plant.

New varieties of potato plant can be produced by selective breeding.

Explain how selective breeding of the two varieties of potato plants can produce new potato plants that are all faster growing and produce many, large potatoes.

Figure 1 shows a plasmid containing the human insulin gene.

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

Figure 1 shows some information about two types of cattle.

Figure 1

Describe how these types of cattle could be selectively bred to produce cattle that can survive high temperatures and have good meat quality.

Figure 2 shows the leaf of a wheat plant with a fungal disease.

Figure 2

Give two benefits of breeding wheat plants that are resistant to fungal disease.

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Figure 1 shows the limbs of some animals.

Figure 1

Describe how these limbs provide evidence for evolution.

Prickly pear cacti are weeds that grow in many countries.

Insects have been used to limit the population of prickly pear cacti.

Figure 2 shows some insects on a prickly pear cactus.

Figure 2

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Some crop plants have been genetically modified to be resistant to insect pests.

Explain the advantages and disadvantages of producing genetically modified crop plants.