Coat color variation in mammals has long served as one of most fruitful examples

Question

Coat color variation in mammals has long served as one of most fruitful examples of genetics, with over 120 loci and 800 alleles affecting coat adaptive transition from color described in mice alone. For this question, we will consider the dark to light coat coloration that accompanied the movement of mice from the species forest to the beach among two species of mouse. The ancestral species was darkly colored while the derived species was more lightly colored, consistent with the selective pressures that come when you are a dark mouse living on lightly colored sand. The phenotypes of the two parental species, along with a representative F1 individual and representatives from the F2 generation are shown below. Assume that you only had the data shown above for the parental lines (ancestral and derived species) and the F1. What inferences would you make about the mode of for the overall (whole body) coat color? Support your inferences clearly [do not just write the mode of inheritance, explain why you arrived at that answer]. With the added data from the F2, what inferences might make about the mode of inheritance for the overall (whole body) coat color? Support your inferences clearly [do not just write the mode of inheritance, explain why you arrived at that answer].

Explanation / Answer

2.1 Ancestral traits are those found in the ancestors of both species and derived traits are traits that exist in a present organism, but did not exist in that organism's ancestors. So here when mouse lived in the forest they were dark coloured and once they moved to beach where there is a light background the survival chances of these mice became dim. So inorder to adapt their coat colour showed variation to a lighter colour. This is a perfect example of epistasis. Genetic basis for this transition is due to interaction between structural changes to to the agouti locus and regulatory changes to the Mc1r locus. Thus the F1 generation produced from ancestral species and derived species will show a different coat colour.

2.2 Overall mode of inheritance of coat colour in F2 generation is directly dependent on their parents and there is no environmental effect. The F2 generation mice will have coat colour varying from derived mice coat colour to F1 mice coat colour. Moreover coat colour is determined by more than 800 alleles and 120 loci.

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