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Name: Amanda E Kulik
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When can mutations be considered helpful?

Mutations are considered helpful if they lead to a trait in the organism that helps it survive better in its environment. Remember, you can't make this judgement at the time the mutation occurred, because the environment may change and the silent, non-harmful mutation might then become helpful. If it is, then individuals carrying the mutation will survive better than those that don't. This is the basis of Darwin's theory of natural selection. First you have genetic diversity in a species, that is to say, different mutations in the genome. Then the environment acts on that diversity to select certain individuals for better survival. In different environments, mutations may have very different effects. For example, the disease sickle-cell anemia is harmful in most parts of the world. It is particularly prevalent among Africans and African-Americans. Why doesn't it just die out? Because in Africa, people with the mutation on just one of the two chromosomes (carriers, or in genetic terminology heterozygotes) are more resistant to malaria, so the mutation is selected for by the environment.


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