[__ Science __ ] Sickle Cell Anemia and Other “Good” Mutations of Evolution

[AIG.com]

The survival of living species depends on its ability to pass on its genetic instructions, from generation to generation, without significant alteration.

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[Barbarian]

Why should the sickle cell gene increase in an area with lots of malaria? Because people who have one copy of the gene in such places, tend to leave more healthy offspring than people who don't. Just that simple.

But if you happen to get two copies of the gene, you probably die before you can reproduce. So there's an optimum level for the gene in any population. But there's selective pressure for a "better fix" than doesn't kill a small number of people in the process.

Enter HbC. HbC works pretty much like HbS, the sickle cell gene, but this mutation doesn't kill off those with two copies of the gene. A clear improvement. Not surprisingly, HbC is increasing in malaria areas.

Hemoglobin C - Wikipedia

en.wikipedia.org

It still can cause mild anemia, albeit much less than HbS or malaria. So it's better, but not perfect. Natural selection is still working...