Question

The frequency of a dominant allele A in a population is P = 0.4, and the rate of a recessive allele a at the same locus is q = 0.6. Assuming that allele a is fatal in double dose (individuals with genotype aa die in the fetus).

a) What happens with the frequencey to the a-allel in the long term?

b) Why will a never completely be gone if the population has infinite size?

Answer 1

Answer a)
In the long term, the frequency of the a-allele will reduce because all aa individuals will die in the fetal stage. Only the Aa individuals will be able to survive.

Answer b)
Allele a will never completely be gone if the population has infinite size because the heterozygote carriers will always be there. When paired with homozygous dominants, there is a 50% chance of producing a carrier. When paired with another heterozygous individual, there is a 50% chance of producing a carrier and 25% chance of producing a homozygous aa individual which would anyway die in the fetal stage.