Question

Directional selection acting upon a favored recessive allele:

a) fixates quickly because heterozygotes do hold an advantage

b) fixates quickly because heterozygotes don't hold an advantage

c) takes time to fixate because heterozygotes do hold an advantage

d) takes time to fixate because heterozgotes don't hold an advantage

e) none of the above

Answer 1

It was scientist Charls Darwin who first described the term directional selection. It is nothing but a type of natural selection where a particular phenotype become permanent dominant over other phenotype and because of that allele frequency gradually shift to the direction of dominant allele. As I mentioned this process is gradual and take time to shift hence overtime frequency shift toward favored allele.

There are some condition because of that natural selection occurs according to Darvin- Like, For some trait if variation is found in the population. Such variation found to be heritable. And variation in such trait if remained associated with variation in fitness of individual.

Allele frequency doesn’t change over time automatic but gene flow, genetic drift and natural selection are the reason behind this. When one of this occurs overtime, the evolution takes place.

Directional selection act upon a favored recessive allele also, because natural selection favor the survivability and favor genotype that are better efficient to survive, a new favored recessive allele also can increase in frequency over a period of time. But the rate of increase in frequency of favored type of allele depend on whether allele dominant of recessive.

Like increase in the number of favored recessive allele depend on the number of people in a population with homozygous recessive allele, and rising the homozygous number in a population takes time so favored recessive allele will increase slowly for many generation until it become common in perticular population and once it achieve enough number it increase rapidly.