Question

Two cats with medium-length tails have a litter which includes 6 with medium tails, 2 with long tails, and 3 with no tails. From these data, we might infer that incomplete dominance is operating here. Explain why this seems to be true and identify the genotypes of all these cats.

Answer 1

Answer: This is a case of incomplete dominance inheritance because we can asume that the tail length is a trait with 2 alleles (no tail and long), but is posible to see 3 fenotypes, long, no tail, and medium which can be consider as a half way between long and no tail.

The phenotypes that seem a mix of two traits have heterozygous genotype, in this case the two parental cats have genotype Ll (assuming L as the symbol for long tail) since they have medium tails

When 2 heterozygous individual cross, the proportions according to Mendel's laws is:

25% offspring: Homozygous dominant

25% offspring: Homozygous recesive

50% offspring: Heterozygous

This proportions are quit similar to those obtained in the exercise

2/11 = 18 % Long tail: LL

3/11 = 27% No tail: ll

6/11 =54% Medium tail: Ll