CDS (I) 2022 General Knowledge · Question 14 of 120

Correct — B, This technique has applications only in plants. Genetic modification is not confined to crops, and the counter-examples are not obscure ones. Human insulin has been made by genetically engineered bacteria since the technique was developed in 1978, with biosynthetic insulin in clinical use from 1982; the gene for human insulin is put into Escherichia coli, and the bacterium manufactures the protein. Before that, insulin for patients had to be recovered from the pancreases of cattle and pigs as a by-product of the meat industry. Transgenic animals are made routinely for research, and the stem's own last option describes how it is done. So the statement that the technique applies only to plants is the one that fails, which is what the question asks for.

• (a)In this technique a gene from one organism is isolated and transferred to the cell of another organism. — A correct statement, and in fact the definition of the technique. Isolating a gene and moving it into a different organism is what makes that organism transgenic, whether the recipient is a bacterium, a plant or an animal.
• (c)Genes for insect resistance may spread from crop plants to wild plants. — Correct, and it is one of the recognised biosafety concerns rather than a hypothetical one. Pollen carries genes to wild and weedy relatives that can cross with the crop, which is why regulators require isolation distances and study gene flow before approving a release.
• (d)To produce a transgenic animal the novel genes are inserted at a very early stage of development. — Correct. The gene must go in early — typically at the fertilised-egg or early-embryo stage — so that it is copied into every cell as the embryo divides, including the germ cells that pass it to the next generation.

Genetic modification means moving a gene from one organism into another so that the recipient makes a product it could not make before. The recipient can be a microbe, a plant or an animal. Bacteria were the first hosts and remain the workhorses, producing insulin, growth hormone and industrial enzymes. In plants the best-known Indian case is insect-resistant cotton carrying a gene from the soil bacterium Bacillus thuringiensis, whose protein is toxic to bollworms. In animals the gene is introduced at the fertilised-egg or early-embryo stage so that every later cell carries it.

A 'not correct' item with three defensible statements and one absolute one is usually settled by the absolute word, and here that word is 'only'. Statements about a technique that claim it works in exactly one kingdom are worth doubting on sight, and a single counter-example is enough to bring this one down. Insulin from engineered bacteria is the easiest to hold on to, because it is both early and familiar. One thing this card does not attempt to settle is which genetically modified crops India permits for commercial cultivation today — that position has moved since the 2022 exam and has been through the courts, so it is worth checking against a current government source rather than against any explanation, including this one. Nothing in the answer depends on it.

• Biosynthetic human insulin has been made by recombinant DNA technology in Escherichia coli since 1978, and has been in clinical use since 1982.
• Before that, insulin for patients came from the pancreases of cattle and pigs.
• Insect-resistant transgenic cotton carries a gene from the soil bacterium Bacillus thuringiensis, whose protein kills bollworms.
• Transgenic animals are made by introducing the gene at the fertilised-egg or early-embryo stage so that all later cells carry it.
• Gene flow from a modified crop to wild or weedy relatives through pollen is a recognised biosafety concern, not a hypothetical one.

• Reading an absolute word such as 'only' past without testing it against a single counter-example.
• Assuming genetic modification began with crops, when bacteria producing insulin came first.
• Treating gene flow to wild relatives as an objection invented by critics rather than a documented biological process.

As a statements item on what the technique is and where it applies, or through a specific case — Bt cotton, golden rice, or a named regulator.

• practice — not a real PYQ

  The gene that makes Bt cotton resistant to bollworm attack was obtained from

  • (a)a soil bacterium
  • (b)a wild variety of cotton
  • (c)a species of fungus
  • (d)an insect predator of the bollworm

  Answer(a) a soil bacterium — Bacillus thuringiensis, whose crystal protein is toxic to the larvae of certain insects.

• practice — not a real PYQ

  Human insulin for medical use is today produced mainly by

  • (a)grinding the pancreas of cattle and pigs
  • (b)chemical synthesis from amino acids in a laboratory
  • (c)genetically engineered bacteria carrying the human insulin gene
  • (d)extracting it from the urine of diabetic patients

  Answer(c) genetically engineered bacteria carrying the human insulin gene — biosynthetic insulin replaced the animal-sourced product from 1982 onwards.