Steps of genetic engineering
Genetic engineering (genetic modification) involves transferring a gene from one organism to another, often across species. The basic steps are:
1. The desired gene is identified and cut from the donor organism's DNA using restriction enzymes (biological scissors that cut DNA at specific base sequences).
2. A vector (carrier) is prepared. This is usually a bacterial plasmid (a small circular piece of DNA), which is also cut open using the same restriction enzyme.
3. The gene is inserted into the plasmid using ligase (an enzyme that joins DNA fragments together).
4. The recombinant plasmid is introduced into a host organism (e.g. A bacterium), which now produces the protein coded for by the inserted gene.
Insulin production as an example
The human insulin gene is cut from human DNA and inserted into a bacterial plasmid. The modified bacteria are grown in large fermenters where they produce human insulin. This insulin is purified and used to treat diabetes.
Advantages include: producing large quantities of insulin quickly, the insulin is identical to human insulin so causes fewer allergic reactions than the animal insulin previously used, and it does not require animals to be killed. This is the most commonly tested example and students should be able to describe the full process.
Cloning organisms
Cloning produces organisms that are genetically identical to the parent. In plants, this can be done through tissue culture (taking small groups of cells from a plant and growing them on nutrient agar with hormones to produce new plants). In animals, nuclear transfer involves removing the nucleus from an egg cell and replacing it with the nucleus from a body cell of the organism to be cloned.
Plant cloning is widely used in agriculture and horticulture to produce many identical copies of plants with desirable characteristics. Animal cloning is more controversial and technically difficult.
Benefits and risks
| Benefits | Risks and concerns |
|---|---|
| Production of useful proteins (e.g. Insulin) | Possible ecological harm if GM organisms escape into the environment |
| Crops engineered for pest resistance or higher yield | Ethical concerns about modifying organisms |
| Cloning preserves desirable characteristics | Cloned animals may have health problems or short lifespans |
| Gene therapy may cure genetic diseases | Reduces genetic diversity in crops |
Exam answers should present both sides with specific examples rather than vague statements like "it is unnatural".