Two cats mated. One of the parent cats is long-haired (recessive allele). The litter which results contains two short-haired and three long-haired kittens. What does the second parent look like, and what is its genotype?

 

If

L=dominant allele (short hair), and l for recessive.

The unknown parent had LI genotype.

Long hair is caused by a recessive allele meaning that the dominant allele cannot be available for it to express phenotypically.

One of the parent cats has long hair and therefore there genotype must be: II (because if L was available it would have had short hair because L is dominant).

This means that it contributes a recessive allele (I) to all off springs because all offspring get to acquire 1 allele from either parent.

Because some of the litter are short haired, they must have gotten a dominant allele (L) from one of the parents.

Those kitten that are long haired must have received a recessive allele (I) from the unknown parent.

What this means is that the unknown parent must have been short haired and had LI.