Question

These little bunnies (A, B, and C) were born in the same litter to the same parents, but they have different traits for the feature of ear thickness. Bunny A has thick ears, bunny B has average ears, and bunny C has thin ears. How did these bunnies end up with ear thicknesses that are different from one another even though they have the same parents? How did the gene combinations result in the different traits?

Answer 1

A simple way to get three different ear-thicknesses from the same parents is incomplete dominance of a single gene.

- Let T = “thick” allele and t = “thin” allele.
- In incomplete dominance, TT = thick, Tt = intermediate (average), tt = thin.

If both parents are heterozygous (Tt, average ears), each parent’s gametes are half T and half t. Random fusion of gametes gives offspring genotypes:

- TT (25%) → thick ears (Bunny A)
- Tt (50%) → average ears (Bunny B)
- tt (25%) → thin ears (Bunny C)

Mechanistically this happens because meiosis in each parent produces different gametes (segregation of alleles) and fertilization randomly combines them, so siblings can inherit different allele combinations even though they have the same two parents.

(Other possibilities can also produce variation — polygenic traits, environmental effects, mutations or different dominance relationships — but the TT/Tt/tt incomplete-dominance model explains the three clear phenotypes you described.)