In a population of rock pocket mice (a small animal), about half the individuals

Question

In a population of rock pocket mice (a small animal), about half the individuals have pale fur and half have dark fur. What is the best explanation for why this variation maintained? O A. The dark fur and the pale fur alleles are codominant. B. Selection against pale individuals is ineffective, because this trait is associated with a recessive allele C. Pale individuals have a selective advantage in some areas and dark individuals have a selective advantage in other areas. D. Individuals with intermediate fur colour (halfway between pale and dark) would have the highest fitness of all phenotypes.

Explanation / Answer

In rock pocket mice, pale fur type survives on sandy soil and dark fur type survives on dark colour rocks. This has occurred due to a mutation in a gene MC1R which regulates the coat colour in the rock pocket mice.

These kind of mice are seen in American southwest deserts where light coloured rocks and sandy soil was common. But after many years volcanoes erupted and black lava came out which covered some parts of the deserts. Pale fur mouse could now easily be predated by owls. So, due to natural selection dark fur mouse survived better.

Just a single copy of variant MC1R is enough to give rise to dark fur colour mice and for pale fur colour mice two such variant copies of MC1R gene variant is needed.

So pale individuals have a selective advantage in some areas and dark individuals have a selective advantage in some other areas.

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