Practise recombinant DNA, gene transfer, PCR, electrophoresis and medical or agricultural applications while interpreting molecular methods and biological data.
Recombinant human proteins can be used to treat disease.
Define the term recombinant DNA.
From the 1920 s until the 1970 s, insulin obtained from the bodies of animals was used to treat diabetes. From the 1970s, recombinant human insulin was used instead.
Explain the advantages of using recombinant human insulin to treat people with diabetes.
Insulin is composed of two polypeptide chains, the A chain and the B chain, that are linked by disulfide bonds.
Variations in amino acid sequence occur:
- in the insulin molecules of different animals
- in new versions of human insulin that have been engineered to control blood glucose concentration more effectively than normal recombinant human insulin. These new versions of human insulin are called analogues.
Table 4.1 shows the amino acid positions where variation occurs in different animal and human analogue insulin molecules. The dashes indicate a missing amino acid.
Suggest ways in which analogue insulin molecules can be produced by genetic engineering techniques.
Information about amino acid and nucleotide sequences is stored in computer databases.
Outline the advantages of using databases of nucleotide sequences to investigate evolutionary relationships between species.
Factor VIII can be made as a recombinant human protein.
Name the disease that is treated using recombinant human factor VIII.
Before recombinant human factor VIII was available, this disease was treated with factor VIII from donated blood.
Give two advantages of using recombinant human factor VIII, instead of factor VIII from donated blood, to treat this disease.
The gene that codes for human factor VIII can be synthesised from messenger RNA purified from human liver cells.
Name the enzyme that uses messenger RNA as a template to produce complementary DNA.
Outline two sources, other than messenger RNA, from which genes can be obtained for genetic engineering.
The gene that codes for human factor VIII can be transferred into mammalian cells in tissue culture.
Explain why a promoter also needs to be transferred into the mammalian cells so that human factor VIII can be synthesised.
Fig. 5.1 shows the area of land that was used to grow genetically modified (GM) crops in the USA, Brazil, India and China from 2004 to 2015.
Fig. 5.1
Suggest reasons why the area of land used to grow GM crops in the USA is greater than the area of land used to grow GM crops in Brazil.
Genetic modifications in crops can provide resistance to insect pests. Bt maize is one type of GM crop that has been produced to be resistant to insect pests.
State two benefits to farmers of insect resistance in crops.
Describe the difference between Bt maize and non-GM maize that explains why Bt maize is resistant to insects.
State two reasons why people may have objections to the growth of insect-resistant GM crops.
In 2015, the percentage of the USA population that objected to the use of GM crops was lower than in 2005.
Suggest why a smaller percentage of the USA population objected to the use of GM crops in 2015.