How would you do a punnett square for double eyelashes if the father is dominant and the mother does not carry the trait?

Answer 1

If you do not know whether the father is homozygous dominant (2 dominant genes) or heterozygous dominant (1 dominant and 1 recessive) you will have to do 2 squares.

If the father is homozygous his genes would be EE

If the father is heterozygous his genes would be Ee

The mother will always be ee

SQUARE 1: EE x ee

E E

e Ee Ee

e Ee Ee

SQUARE 2: Ee x ee

E e

e Ee ee

e Ee ee

In square 1, all of the children will be heterozygous dominant for double eyelashes and will carry the trait

In square 2, 50% of the children will be heterozygous dominant for double eyelashes and carry the trait, and 50% of the children will have recessive genes and not carry the trait at all.

Answer 2

If the father is dominant for double eyelashes (we'll use D for the dominant allele) and the mother does not carry the trait (we'll use d for the recessive allele), all offspring will have a heterozygous genotype with one dominant allele from the father and one recessive allele from the mother (Dd). Therefore, the Punnett square would show 100% of the offspring having double eyelashes.