Question

In chickens, the black (B) and white (W) alleles for feather color are codominant. If a homozygous white chicken is crossed with a homozygous black chicken, the offspring has feathers that are both black and white, a trait that is known as erminette. The Punnett square shows the possible genotypes resulting from the cross of an erminette chicken with a white chicken.Select the correct answers to indicate the expected percentage of offspring with each phenotype resulting from the cross shown in the Punnet square. The expected phenotypes of offspring with BLACK, WHITE and ERMINETTE phenotypes are:A. 0%B. 25%C. 33%D. 50%E. 66%F. 75%G. 100%

Answer 1

As the pattern observed is of codominance, the chicken will be white or black only when its homozygous (WW - white, BB - black). When it's heterozygous (WB) there will be a mix of white and black feathers.

The Punnet square shows that when an erminette chicken (WB) crosses with a white chicken (WW), half of the offspring will be BW (erminette) and the other half will be white (WW). There will be no black chickens, because for that we would need both of the parents to have the B allele, so the offspring would include black chickens (BB), but only the erminette one does have it.

So, considering that 1/2 of the offspring is erminette (BW) and 1/2 of the offspring is white (W), we can say that the expected phenotypes are:

BLACK - 0%

WHITE - 50%

ERMINETTE - 50%