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Transgenics

Transgenics refers to the movement of genes between organisms of different species.

The transferred gene is called a transgene. Transgenes can alter the phenotype of the receiver.

A transgene can be used by the cell to produce a new protein that the cell could not make before.

There are two important types of transgenics to be aware of:

  • Natural transgenics: Bacteria are capable of transferring genetic material between individuals without reproducing. This is called conjugation.
  • Human uses of transgenics: Scientists are able to create transgenic bacteria, flies and mice! This is called genetic engineering.
Transgenics has been used to make mice that produce fluorescent proteins. They glow under UV light!
Transgenics has been used to make mice that produce fluorescent proteins. They glow under UV light!

Genetic engineering uses transgenics to generate organisms with desired phenotypes.

A plasmid is a small, circular DNA molecule in bacteria. Scientists use plasmids to add useful genes into other bacteria, plants and even animals:

Genetic engineering is used to produce human insulin protein on an industrial scale. Insulin is required for the treatment of diabetes mellitus.

The human insulin gene has been inserted into bacteria using genetic engineering. These bacteria now produce human insulin. The bacteria are grown in a fermenter:

Fermenters keep bacteria under optimal growth conditions to maximise the production of insulin.
Fermenters keep bacteria under optimal growth conditions to maximise the production of insulin.

There are several advantages to this method of insulin production:

  • Human insulin: the old method of insulin production used insulin from pigs or calves. This can cause an immune reaction and has ethical objections.
  • Large-scale production: the bacteria are grown in vast amounts.
  • Purer product: the bacteria secrete the insulin, making it very easy to separate from the bacteria and harvest.
  • Much cheaper: the process is roughly 1% of the cost of extracting insulin from a pig pancreas.

Genetic engineering has been a topic of fierce ethical and moral debate. It is important to understand both sides of the discussion.

The table gives some examples of advantages and disadvantages. It is not a complete list.

Advantages Disadvantages
Large-scale production of gene products, e.g. insulin Potential for creating new harmful diseases or biological weapons
Potential for treatment of genetically inherited diseases Potentially harmful side effects with lesser known genes.
Development of disease-resistant crops with increased yield. Could help fight world food shortage Danger of introduced transgenes being transferred to other organisms.
Production of fortified foods, e.g. golden rice is enriched with beta carotene. Some people do not like the idea of eating genetically modified foods.
There have been many protests against the use of genetically modified organisms.
There have been many protests against the use of genetically modified organisms.

Bacterial conjugation is the mechanism used by bacteria to transfer genes from one organism to another.

Some genes in bacteria are stored in plasmids; a small, circular DNA molecule. Plasmids can replicate separately from the rest of the DNA. They can easily move from one cell to another.

The image below summarises the main steps in conjugation: