Question

In Siamese cats, enzymes that code for dark fur color are only active in cooler temperatures. Thus, the tips of a Siamese cat's ears, feet, and tail are dark but not the warmer regions of its body core. This is an example of _____

a) Epistasis
b) Incomplete dominance
c) Pleiotropy
d) Temperature-dependent expression

Answer 1

The dark fur color in Siamese cats, influenced by cooler temperatures on the extremities, is an example of temperature-dependent expression. This differs from epistasis, incomplete dominance, and pleiotropy which involve genetic interactions, blended phenotypes, and single genes affecting multiple traits, respectively.

Step-by-step explanation:

In Siamese cats, the dark fur color is produced by enzymes that are only active at cooler temperatures. This leads to the characteristic dark coloration of the ears, feet, and tail, while the warmer body core remains a lighter color. This phenomenon is an example of temperature-dependent expression, where the environment (in this case, temperature) affects the expression of a genetic trait. This is a different concept from epistasis, which is an interaction between different genes where one gene masks or modifies the effect of another gene, as seen in the case of mouse coat color genetics. Incomplete dominance occurs when two alleles produce a phenotype that is a blend of both alleles, and pleiotropy refers to a single gene impacting multiple traits.