Question

In tigers, a recessive allele of a particular gene causes both an absence of fur pigmentation (a white tiger) and a cross-eyed condition. If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? What percentage of cross-eyed tigers will be white?

Short answer

The mating of two normal heterozygous tigers gives rise to a 25% cross-eyed offspring.

The offspring, which are cross-eyed tigers with white color fur, occur with 100% due to pleiotropic genes.

Step-by-step solution

Description of pleiotropy

Pleiotropy is a phenomenon in which a single gene is responsible for different types of phenotypic characters. The phenotypic traits that are controlled by the pleiotropic genes are unrelated to each other.

Percentage of cross-eyed tigers in offspring

The recessive allele is responsible for fur pigmentation and cross-eyed condition. This exhibits the condition that occurs when both the recessive alleles are present.

The tigers are heterozygous with the pleiotropic condition. Thus, the genotype of the tigers must be Pp as the tigers are phenotypically normal and are not cross-eyed or white. The Punnett square for the tiger's cross is as follows.

	P	p
P	PP	Pp
p	pP	pp

P-normal pigmentation

p-white

After mating, the condition arises, which is one in four chance of white color and cross-eyed. Thus, the possibility is ¼ that is equal to 25%.

Percentage of a cross-eyed tiger with white fur pigmentation

A single gene is responsible for the condition of cross-eyed tiger and fur pigmentation as white color. After mating, the offspring that are cross-eyed will be white. The possibility is 100% due to the pleiotropic property.