Clouded leopards are a medium-sized, endangered species of cat, living in the very wet cloud forests of Central America. Assume that the normal spots (XN) are a dominant, sex-linked trait and that dark spots are the recessive counterpart.

Question

Clouded leopards are a medium-sized, endangered species of cat, living in the very wet cloud forests of Central America. Assume that the normal spots (XN) are a dominant, sex-linked trait and that dark spots are the recessive counterpart.

Suppose, as a Conservation Biologist, you are involved in a clouded leopard breeding program. One year you cross a male with dark spots and a female with normal spots. She has four cubs and, conveniently, two are male and two female. One male and one female cub have normal spots and one each have dark spots.

What is the genotype of the mother for this sex-linked trait?

a
heterozygous
b
impossible to determine with given information
c
purebred for normal spots
d
homozygous

Answer 1

Based on the information given, the genotype of the mother for this sex-linked trait can be determined as heterozygous (option a). This can be inferred because one male and one female cub have normal spots, indicating that they received the dominant allele for normal spots from their mother. Since the trait is sex-linked, the mother must pass on the X chromosome to her offspring, and since half of her offspring have normal spots, it suggests that she carries both the dominant and recessive alleles for the spots. Therefore, her genotype for this sex-linked trait is heterozygous.