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Must-know facts
20 facts
- 1Three research areas: superior catalyst (organism or pure enzyme), optimal conditions for it, downstream processing.
- 2Three routes to more food: agro-chemical, organic, and GM crop-based agriculture; the Green Revolution tripled food supply.
- 3Totipotency: any cell or explant can regenerate a whole plant; micro-propagation gives genetically identical somaclones.
- 4Tissue culture medium: sucrose as carbon source, inorganic salts, vitamins, amino acids, auxins and cytokinins.
- 5Virus-free plants come from the meristem (apical and axillary), which stays free of virus; banana, sugarcane, potato.
- 6Protoplast fusion gives somatic hybrids; tomato + potato gave the pomato, which was not commercially useful.
- 7Golden rice is vitamin A enriched rice.
- 8Bt toxin is an inactive protoxin; the insect's alkaline gut pH solubilises the crystal and activates it; it makes pores in midgut epithelial cells.
- 9Bt proteins act on lepidopterans, coleopterans and dipterans; cryIAc and cryIIAb control cotton bollworms, cryIAb controls corn borer.
- 10RNAi against Meloidogyne incognita in tobacco: Agrobacterium vectors, sense + anti-sense RNA form dsRNA that silences nematode mRNA.
- 11About 30 recombinant therapeutics approved worldwide; 12 marketed in India.
- 12Insulin: chains A and B joined by disulphide bridges; pro-insulin carries a C peptide removed at maturation.
- 131983, Eli Lilly: A and B chain DNA put in E. coli plasmids, chains made separately and joined by disulphide bonds.
- 14First clinical gene therapy: 1990, a 4-year-old girl with ADA deficiency; lymphocytes + ADA cDNA via retroviral vector; periodic infusion needed.
- 15PCR detects pathogens at very low concentration and is routine for HIV; radioactive probes + autoradiography; ELISA uses antigen-antibody interaction.
- 16Over 95 per cent of transgenic animals are mice.
- 17Rosie (1997), the first transgenic cow: milk with human alpha-lactalbumin, 2.4 grams per litre.
- 18Human α-1-antitrypsin from transgenic animals treats emphysema; transgenic mice test polio vaccine safety.
- 19GEAC = Genetic Engineering Approval Committee; decides on GM research and release.
- 20Basmati patent 1997 by an American company; India has about 200,000 rice varieties and 27 documented Basmati varieties.
Common traps
Where marks are lost
Saying Bt toxin does not kill the bacterium because the bacterium is resistant to it.
The toxin is stored as an inactive protoxin; only the alkaline gut of the insect activates it.
Saying the protoxin is activated by the acidic pH of the insect gut.
The insect gut is alkaline; the alkaline pH solubilises the crystal and activates the toxin.
Pairing cryIAb with cotton bollworm.
cryIAc and cryIIAb control cotton bollworms; cryIAb controls the corn borer.
Thinking RNAi in the tobacco plant kills the nematode with a toxin protein.
The plant makes dsRNA that silences a specific nematode mRNA, so the parasite cannot survive; no toxin protein is involved.
Writing that Eli Lilly's E. coli made pro-insulin with the C peptide.
Separate DNA for chains A and B was used; the chains were made separately and joined by disulphide bonds, so no C peptide was involved.
Calling ADA gene therapy with lymphocytes a permanent cure.
Lymphocytes are not immortal, so infusions are repeated; only a gene put into early embryonic cells could be permanent.
Saying somaclones are genetically varied.
Micro-propagated plants are genetically identical to the parent; that is what somaclone means here.
Taking the whole infected plant for virus-free culture.
Only the apical or axillary meristem is virus-free, so the meristem is cultured.
Expanding GEAC as Genetic Engineering Advisory Committee.
It is the Genetic Engineering Approval Committee.
Key terms
18 terms
- Explant
- Any plant part taken out and grown in a test tube on a sterile nutrient medium.
- Totipotency
- The ability of a single cell or explant to regenerate a whole plant.
- Micro-propagation
- Producing thousands of plants quickly by tissue culture.
- Somaclone
- A tissue-culture plant genetically identical to the parent it came from.
- Protoplast
- A plant cell whose wall has been digested away, bounded only by the plasma membrane.
- Somatic hybridisation
- Fusing protoplasts of two varieties and growing the hybrid cell into a plant.
- GMO
- An organism whose genes have been altered by manipulation.
- Bt toxin
- Insecticidal protein of Bacillus thuringiensis, stored as an inactive protoxin crystal.
- cry gene
- A gene coding for a Bt crystal toxin protein, such as cryIAc or cryIAb.
- RNA interference
- Silencing of a specific mRNA by a complementary double-stranded RNA that blocks its translation.
- C peptide
- The extra stretch in pro-insulin, removed when it matures into insulin.
- Gene therapy
- Correcting a gene defect by delivering a normal gene into a person's cells or an embryo.
- ADA deficiency
- Immune disorder caused by deletion of the gene for adenosine deaminase.
- Probe
- A radioactively tagged single-stranded DNA or RNA that finds its complementary sequence.
- ELISA
- Enzyme Linked Immuno-sorbent Assay: detects infection by antigen-antibody interaction.
- Transgenic animal
- An animal whose DNA has been manipulated to carry and express a foreign gene.
- GEAC
- Genetic Engineering Approval Committee, which rules on GM research and release in India.
- Biopiracy
- Using a country's bio-resources without authorisation and without compensatory payment.