Explain how a recessive allele that is fatal to a homozygous individual can remain in a population without kil

Question

Explain how a recessive allele that is fatal to a homozygous individual can remain in a population without kil

Answer 1

Peter S is not wrong, but that's only true for rare cases. Most fatally recessive diseases doesn't give any advantage at all in their heterozygous form, but they don't do any harm either. And that's the reason they stay in the population. Evolution needs something to work on, and if a gene neither gives advantage or disadvantage only chance will work on it. That two copies of it is fatal doesn't matter, evolution can't think forward in that way. So as long as just one allele isn't harmful it can keep being passed on to the next generation with the same frequency as all other neutral genes.

Answer 2

Because in the heterozygous state an advantage is conferred.

Eg Sickle cell trait is heterozygous Ss & sickle cell anaemia is homozygous ss.

The heterozygotes have an advantage in a malaria area since they have some resistance to the parasite and tend to survive and the genes will be passed on - both the normal allele (S) and the recessive allele (s) thus maintaining the recessive allele in the population.

Answer 3

Dominant allele overrides it.....put simply.

Answer 4

As long as heterozygotes don't get disease (or get less severe disease that does not hinder their ability to reproduce), the disease allele can remain in the population.

Sickle cell is a special example because not only are the heterozygotes free of sickle cell disease, but they are also less likely to die from malaria.

Cystic fibrosis is similar in that heterozygotes may be more resistant to cholera.