The big idea: In gene knockout a gene is deliberately changed so it is inoperative. Comparing the knockout organism with a normal one shows what the gene does.
The points to remember
- Knockout: a gene is altered on purpose so that it no longer works.
- With the gene knocked out, no working protein is made from it.
- Scientists compare the phenotype of knockout and normal organisms.
- The differences reveal the function of the gene.
- Libraries of knockout organisms are available for model species such as mice.
Remember it as: No gene, no protein: what goes wrong tells you what it did.
Real example: myostatin. Mice with the myostatin gene knocked out grow about twice the normal muscle mass. This showed that myostatin's job is to limit muscle growth.
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Libraries of knockout organisms: For some model species, collections of knockout organisms already exist, one gene at a time.
Why they help research
- Model organisms such as mice, fruit flies and yeast share many genes with humans.
- An international project aims to knock out each of the roughly 20,000 mouse genes in turn.
- Researchers can order a knockout instead of making it, saving years of work.
- Knockouts are used to study diseases, such as cancer in p53 knockout mice, and to test drugs.
Knockout is not therapy: Knockout organisms are for finding out what genes do. They are not used to treat patients.
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How it is asked: 1A items on what knockout is used for or how knockout mice help research, and a Describe [4] on gene knockout in research.
IB-style questionDescribe[4 marks]
Describe the use of gene knockout technology in research.
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