Recombinant human proteins can be used to treat disease.

1. (a)(i)Define the term recombinant DNA.[1]
2. (a)(ii)From the 1920s until the 1970s, 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.[3]
3. (b)(i)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. Cats with diabetes can be successfully treated with insulin injections. Cat insulin is not available, but vets can choose from the other types of insulin shown in Table 4.1. Identify the type of insulin that is most suitable for treating cats.[1]
4. (b)(ii)Suggest ways in which analogue insulin molecules can be produced by genetic engineering techniques.[3]
5. (c)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.[3]