Genetic Modification (Genetic Engineering)

Hepatitis B is a viral infection that can be deadly in some cases. 

There is a vaccine to prevent infection with hepatitis B that is produced from genetically modified (GM) yeast cells.

The process of producing these GM yeast cells is outlined in the diagram below.

Identify the new protein produced by the yeast cells in the fermentation tank.

(1)

(3)

Explain why enzyme 1 is used to cut both the desired gene and the plasmid DNA in the process shown in part (a).

One mechanism by which the hepatitis B virus can be transmitted is from an infected mother to their baby. This can lead to the infant developing what is known as a chronic hepatitis B infection after birth.

One way of reducing the risk of chronic infection in infants is the use of a hepatitis B vaccine. These vaccines can be produced using proteins produced by yeast cells, as shown in part (a) above, or using proteins isolated from the blood plasma of individuals who have previously been infected with hepatitits B.

Suggest two advantages of producing heptatitis B vaccines using yeast-derived protein rather than plasma-derived protein.

The efficacy of yeast-derived and plasma-derived hepatitis B against chronic heptatitic B infection in infants was studied.

Some of the results are shown in the graph below.

Calculate the percentage increase in infants with chronic heptatitis B, for infants given the plasma-derived vaccine, between 1 and 9 months.

(2)

Describe the effect of the GM yeast-derived vaccine compared to the effect of the plasma-derived vaccine on chronic hepatitis B in infants.

(3)

As part of a global scientific push to improve the efficiency and sustainability of agriculture, scientists have developed a transgenic pig. The process used to create the transgenic pig, known as 'Enviropig', is summarised below.

1. Genes are taken from E. coli bacteria and also from mice.
2. The combined E. coli and mouse genes are inserted into a fertilised pig egg cell nucleus using a microscope and a very small, sharp, pipette.
3. The newly modified egg cell divides and develops into an embryo.
4. The embryo is implanted into the uterus of a surrogate pig and allowed to develop to maturity.
5. The resulting piglet is a transgenic 'Enviropig' that is able to produce E. coli and mouse proteins.

Explain why a plasmid vector is not a suitable way of inserting the desired genes into the fertilised pig egg cell in step 2.

(2)

Explain why all of the cells in the pig embryo that develops in step 3 contain the new genes.

(2)

Separate: Biology Only

Use your knowledge of the role of DNA to explain why the piglet in step 5 is able to produce E. coli and mouse proteins.

(2)

The genes inserted into the genome of 'Enviropig' allow pigs to produce an enzyme called phytase in their saliva. Phytase enables the pigs to digest phosphorus, a mineral that is required in the diet of pigs, but that would otherwise be egested by pigs in their faeces.

Pigs that are unable to produce their own phytase need to take phytase supplements in their food, and still egest a large amount of phosphorus in their waste.

Note that phosphorus is a mineral often found in industrial fertilisers.

Use the information provided and your own knowledge to discuss the potential benefits of 'Enviropig'.

The graph below shows the phosporus levels in the faeces of pigs with different percentages of soybean meal in their diet.

Calculate the percentage decrease in faecal phosphorus between non-transgenic and transgenic pigs on a diet of 54 % soybean meal.

(2)

An environmental science student read the results of the study shown in part (c) and reached the following conclusion:

"In the future, 'Enviropigs' will provide a solution to the sustainability issues around pig farming worldwide"

Evaluate the student's conclusion.

The diagram shows the process of genetic modification used to produce multiple copies of a protein from a desired gene.

Identify structures W-Z in the diagram using the words below. Note that more words have been provided than are needed.

Recombinant DNA     DNA Ligase      Transgenic organism     

Bacterial plasmid      Desired gene      Insulin protein      

Identify the vector used in this genetic modification process.

The enzyme used at both W and X in the diagram in part (a) is a restriction enzyme.

Describe the role of the restriction enzyme at W and X.

Describe what needs to happen to structure Z in part (a) in order to produce many copies of the protein coded for by the desired gene.

The process of genetic modification involves the use of enzymes that cut DNA.

Name the enzymes that are used to cut DNA.

(1)

Explain why the enzymes named in part (i) are so useful in genetic modification.

(2)

Genes can be extracted from other species and inserted into crop plants. For example, a gene that codes for the bacterial toxin known as Bt provides resistance to insect pests in crops.

Other than pest resistance, give two reasons for inserting genes from other species into crop plants.

(2)

(ii)

Suggest why inserting DNA into plant cells can be a challenge.

(1)

Some environmentalists are concerned about inserting Bt toxin genes into crop plants.

Suggest why some are concerned about the insertion of genes from other species, such as the gene for Bt toxin, into crop plants.

Plants can be genetically modified (GM) to produce insect poison.

They are modified using a bacterium called Agrobacterium.

This bacterium has a plasmid that contains recombinant DNA.

Describe how the plasmid is modified to contain recombinant DNA.

A farmer can use either of these methods to improve his crop yield.

• Grow GM plants that produce the insect poison
• Grow non-GM plants and use pesticides

The farmer decides to grow the GM plants rather than using pesticides.

Discuss the decision made by the farmer.