Recombinant Medicines, Gene Therapy and Transgenic Animals: Quick Revision

A brief note on Recombinant Medicines, Gene Therapy and Transgenic Animals. Read it before a test. Try each question at the end before you open its answer.

Recombinant insulin and vaccines

• Gains: recombinant therapeutics can be made in large amounts and do not cause the unwanted immune reactions of products from non-human sources.
• Insulin: chains A and B joined by disulphide bridges. The pro-hormone has the C peptide, which is removed when it matures.
• 1983, Eli Lilly: DNA for chains A and B in plasmids of E. coli. The chains were made separately, extracted and joined by disulphide bonds.
• Vaccine: the hepatitis B vaccine is produced from yeast. It holds a protein of the virus and no whole virus.

Gene therapy and diagnosis

• Gene therapy: a normal gene is delivered to take over from a non-functional one.
• First case, 1990: a four-year-old girl with ADA deficiency, which is caused by the deletion of the gene for adenosine deaminase.
• Steps: lymphocytes are taken, grown outside the body, given a functional ADA cDNA by a retroviral vector, and returned. They are not immortal, so the infusions are repeated.
• Permanent cure: the gene put into cells at an early embryonic stage.
• Diagnosis (not in the NEET syllabus text): PCR copies a little nucleic acid. A probe pairs with its complementary DNA and is seen by autoradiography. ELISA uses an antigen and an antibody.

Transgenic animals

• Meaning: an animal with an extra, foreign gene. Over 95 per cent are mice.
• Five uses: normal physiology and development, study of disease, biological products, vaccine safety, chemical safety testing.
• Examples: alpha-1-antitrypsin for emphysema. Rosie, in 1997, made milk with human alpha-lactalbumin, 2.4 grams in a litre. Transgenic mice may replace monkeys in the polio vaccine test.

A worked example

A transgenic cow gives 20 litres of milk in a day. Each litre has 2.4 g of a human protein. How much protein is in 5 days?

1. In a day: $20 \times 2.4 = 48$ g.
2. In 5 days: $48 \times 5 = 240$ g.

Practice with new numbers

A program to try

The program matches each product with its use.

Mistakes to avoid

• Putting the C peptide in mature insulin. It is removed.
• Joining the chains by peptide bonds. They are joined by disulphide bridges.
• Saying that gene therapy cures for ever. The cells are not immortal.
• Saying that toxicity animals are less sensitive. They are more sensitive.

Check yourself

1. What does the pro-hormone of insulin have that mature insulin lacks?

2. Which gene is deleted in ADA deficiency?

3. Which vaccine is produced from yeast?

4. Which animal is the most common transgenic animal?

Sources

• OpenStax Biology 2e, chapter 17, Biotechnology and Genomics.
• NCERT (2023). Biology, Textbook for Class XII, chapter 10, Biotechnology and Its Applications.