Tail length in mice varies within a population. Scientists observed change in the distribution of tail lengths in a mouse population over time. At the genetic level, what has most likely happened to the allele for the shortest tail lengths?

Not passed along or it is recessive

Explanation:

There are two reasons for the shift in tail length in mice. The first reason could be that the tail length of mice is a recessive trait. In a population where there are also dominant traits, these traits may not show but still be in the population via the heterozygous individuals. The second reason that there may be fewer mice with short tails is that this phenotype causes some survival incompatibility that they may not survive to reproductive years or are not chosen by other mice to cross with. The short tail then does not get passes on.