Biotechnology and its Applications

Biotechnology in agriculture

Three ways to grow more food:

1. Agrochemical-based agriculture (fertilisers and pesticides)
2. Organic agriculture
3. Genetically engineered crop-based agriculture (GM crops)

What are GMOs?

Benefits of GM plants:

• They tolerate stresses such as cold, drought, salt and heat.
• They need fewer chemical pesticides.
• They reduce losses after harvest.
• They use soil minerals more efficiently.
• They can give more nutritious food, e.g. Golden Rice (rich in vitamin A).

Bt cotton: a plant that protects itself

• Bt = Bacillus thuringiensis, a soil bacterium that makes a protein toxic to certain insects.
• The Bt gene was put into cotton, so the plant makes the toxin itself and kills pests that eat it.

How the Bt toxin kills insects

1. The bacterium makes the toxin as an inactive protoxin (crystal protein).
2. An insect eats the plant.
3. The alkaline pH of the insect gut dissolves the crystals.
4. The protoxin becomes an active toxin.
5. The toxin binds the midgut lining and makes pores.
6. The cells swell and burst → the insect dies.

Bt genes (called cry genes):

Pest-resistant plants using RNA interference (RNAi)

• Problem: the nematode (roundworm) Meloidogyne incognita attacks tobacco roots and reduces the crop.
• Solution: RNA interference (RNAi), a natural defence method found in all eukaryotes.

1. Nematode-specific genes are put into tobacco using Agrobacterium.
2. The plant makes both sense and antisense RNA.
3. These pair up to form double-stranded RNA (dsRNA).
4. When the nematode feeds, the dsRNA silences its matching mRNA.
5. The needed protein is not made → the nematode dies.

Biotechnology in medicine

1. Genetically engineered insulin

• Insulin controls blood sugar. Diabetic patients need insulin injections.
• Earlier, insulin came from the pancreas of slaughtered cattle and pigs, which caused allergies in some patients.
• Insulin structure: 2 short chains, A and B, joined by disulphide bridges.
• In the body it is first made as pro-insulin, which has an extra piece called the C-peptide. The C-peptide is removed to make mature insulin.

1. DNA sequences for chain A and chain B are made separately.
2. Each is put into an E. coli plasmid.
3. E. coli makes chain A and chain B.
4. The chains are extracted and joined by disulphide (S–S) bonds.
5. Result: human insulin (Humulin).

• Made in 1983 by the US company Eli Lilly.

2. Gene therapy

• First used in 1990 on a 4-year-old girl with ADA (adenosine deaminase) deficiency. ADA is an enzyme needed for the immune system to work.

1. Lymphocytes are taken from the patient's blood.
2. They are grown in the lab.
3. A working ADA gene is inserted using a retrovirus vector.
4. The cells are put back into the patient.
5. This is not permanent: lymphocytes die, so the treatment must be repeated.

• Permanent cure: put the ADA gene into bone marrow cells at an early embryonic stage.
• Other treatments for ADA deficiency: bone marrow transplant and enzyme replacement therapy.

3. Molecular diagnosis

• Normal tests find a disease only after symptoms appear, when there are many germs.
• New techniques detect it early, when there are very few germs or small changes:
  • PCR: copies tiny amounts of germ DNA until it can be detected (e.g. HIV in suspected AIDS patients, cancer gene mutations).
  • ELISA: based on antigen–antibody reactions (e.g. HIV test).
  • Probes + autoradiography: a radioactive single-stranded DNA/RNA probe sticks to the matching DNA. A mutated gene won't show up on the photographic film because the probe can't bind to it.

Transgenic animals

Transgenic animals have a foreign gene added to their DNA. More than 95% of all transgenic animals are mice.

Ethical issues

• GEAC (Genetic Engineering Approval Committee): an Indian government body that checks whether GM research is valid and whether GM organisms are safe for public use.

Biopiracy

• Basmati rice: India has 27 documented varieties of Basmati. In 1997, an American company (RiceTec) got a patent on Basmati rice and grain in the USA.
• Turmeric and neem were also patented abroad, even though Indians had used them for centuries.
• India has about 2,00,000 varieties of rice alone.
• India's Parliament passed the second amendment of the Indian Patents Bill to stop this.

30-second revision

• GM crops: stress-tolerant, fewer pesticides, Golden Rice (vitamin A).
• Bt toxin: inactive protoxin → alkaline gut → pores → death. cryIAc/cryIIAb → bollworm; cryIAb → corn borer.
• RNAi: dsRNA silences Meloidogyne incognita mRNA in tobacco.
• Insulin: chains A and B made separately in E. coli (Eli Lilly, 1983).
• Gene therapy: ADA deficiency (1990), lymphocytes + retrovirus.
• Molecular diagnosis: PCR, ELISA, probes. Rosie (1997): human α-lactalbumin.
• GEAC checks GM safety; biopiracy: Basmati, turmeric, neem.