You Discover a New Allele of a Gene Important for Tail

Multiple Choice

You discover a new allele of a gene important for tail formation in mice. WT mice have long tails, but mice heterozygous for the allele have short tails. When you cross two heterozygous mice together, you obtain a 2:1 ratio of short- tailed mice to long- tailed mice. None of the short- tailed progeny are homozygous. What type of allele results in short tails?

A) temperature- sensitive allele
B) lethal allele
C) incompletely penetrant allele
D) partially dominant allele
E) dominant negative allele