Biology
In: Biology
For some genetic diseases, notably sickle cell anemia and cystic fibrosis, a single copy of the gene is protective. The sickle cell gene protects against malaria, cystic fibrosis against cholera. In populations at risk from those diseases, those genes strike a balance in the population between how many people are better off due to having a single copy of the gene versus how many are harmed by having both copies.
So that’s why. Kids get those diseases because they’re unfortunate enough to have two carrier parents with the modified gene, AND to have inherited that version of the gene from both parents.
Malaria is so nasty that there are at least two other genetic diseases that protect against it, favism and thalassemia.
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