What is genetic modification?
Genetic modification (genetic engineering) means changing an organism's genetic material by inserting a gene from another organism. Because the genetic code is universal, a gene from one species still works in another.
Key idea
The tools used are: restriction enzymes to cut DNA at specific points, a plasmid (a small circular loop of bacterial DNA) as a vector to carry the gene, and ligase to join the pieces of DNA together.
Making human insulin
Worked example
1) The human insulin gene is cut out using a restriction enzyme. 2) A bacterial plasmid is cut open with the same enzyme. 3) The gene is inserted and sealed in with ligase, forming recombinant DNA. 4) The plasmid is put back into a bacterium. 5) The bacteria multiply in a fermenter, each making human insulin, which is then purified.
GM crops and issues
Crops can be modified for herbicide resistance, insect resistance, or extra nutrients - for example Golden Rice is engineered to contain beta-carotene (a source of vitamin A).
Remember
- Advantages: higher yields, medicines like insulin produced cheaply and in large amounts, added nutrients.
- Concerns: possible effects on wild species, spread of modified genes, and ethical worries.
Genetic modification works only because the DNA code is the same in every organism, so a human gene is read correctly by a bacterium's ribosomes. The same techniques let scientists produce other proteins such as human growth hormone, and give animals or crops entirely new characteristics. However, once released, modified genes cannot easily be recalled, so GM crops are tested carefully and their use is regulated by law in most countries.