Two-hit hypothesis

The Two-hit hypothesis (pronunciation: /tuː hɪt haɪˈpɒθɪsɪs/) is a genetic theory that explains the mechanism behind the onset of certain types of genetic disorders and cancers.

Etymology

The term "Two-hit hypothesis" was first proposed by Alfred Knudson in 1971. The "two hits" refer to the two genetic alterations or "hits" that are required for a cell to become cancerous.

Explanation

According to the Two-hit hypothesis, both alleles of a tumor suppressor gene must be inactivated or "hit" in order for an effect to be seen. The first "hit" is usually a germline mutation that is present in all cells of an organism from birth. The second "hit" is a somatic mutation that occurs in a single cell during the life of the organism.

Related Terms

Knudson's hypothesis: Another name for the Two-hit hypothesis, named after the scientist who proposed it.
Tumor suppressor gene: A gene that regulates cell division and prevents the formation of tumors.
Germline mutation: A mutation that is present in the egg or sperm cells and can be passed on to offspring.
Somatic mutation: A mutation that occurs in a body cell and cannot be passed on to offspring.

External links

Medical encyclopedia article on Two-hit hypothesis
Wikipedia's article - Two-hit hypothesis

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Two-hit hypothesis