[ExI] biology term

[rex]

William Flynn Wallace <foozler83 at gmail.com> [2016-10-12 14:35]:
>    Is the protection against tuberculosis active where there is
>    heterzygosticity, or only when the person has two copies and thus Tay
>    Sachs?  I guess the same question pertains to sickle cell anemia and
>    malaria.  Anybody know?

Implied in the term "balancing selection", is that there is a an
optimal balance in a given environment. In an environment with a low
incidence if sickle cell, there is virtually no advantage to carrying
the gene (nothing to protect against) and a small chance of getting
two copies of the gene and developing sickle-cell. The result is that
in regions where malaria is rare, the sickle-cell gene is rare, and
vice-versa.

Tay sachs and some other genetic issues common in Ashkenazi Jews are
related to superior mental ability as well as protection against TB.

TANSTAAFL.

-rex
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