heterozygotes

The real reason is that these genes sit on the x chromosome, which makes it possible for women to be heterozygotes.

This is the first time I've read about a clotting disorder being beneficial for heterozygotes besides sickle cell.

It's the same allele, of course, heterozygotes get the benefit, homozygotes get the disease.

For instance genes that are only beneficial in heterozygotes would be pruned out.

Although, there are some in Africa who do have fewer chances of acquiring it due to them being heterozygotes for sickle cell anemia.

Individuals who are rs762551(A;C) heterozygotes or rs762551(C;C) homozygotes are both considered slow metabolizers.

It also happens that heterozygotes of TD have higher myelin density.

What are us poor sickle cell heterozygotes to do?

This is because seedling apples are 'extreme heterozygotes'.

We know there are rare genes of large effect because Ashkenazim have at least two, the ones that lead to torsion dystonia and Tay-Sachs disease lead to greater IQ in heterozygotes.

Unlike the Fugate family's hemoglobinopathy, which likely did not provide any benefit, these two do provide some benefit to heterozygotes, and thus end up existing at a steady state in the population.

While some genetic conditions are most common in certain racial groups, I cannot think of any set of genes where heterozygotes are only formed by mating across racial groups.

Apparently they're "extreme heterozygotes", which means their evolved tactic is to really roll the dice hard with each generation, and so they don't "breed true".

Apples are particularly bad, as they're "extreme heterozygotes".

This is because seedling apples are an example of "extreme heterozygotes", in that rather than inheriting genes from their parents to create a new apple with parental characteristics, they are instead significantly different from their parents, perhaps to compete with the many pests.