A maternal effect gene exist in dominant A (normal) allele and recessive a (abnormal) allele. What would be the ratios of genotypes and phenotypes for the offspring of the following crosses?
a. aa female × AA male
b. AA female × aa male
c. Aa female × Aa male
a. All offspring would be Aa, with a normal phenotype. This is because the aa female would only contribute the recessive a allele to her offspring, but it would not have an effect on their phenotype since they would have a normal dominant A allele from the father.
b. All offspring would be Aa, with a normal phenotype. This is because the AA female would only contribute the dominant A allele to her offspring, but her genotype would not affect their phenotype since the maternal effect gene is not linked to the mother's dominant A allele.
c. The genotypic ratio would be 1:2:1 for AA:Aa:aa, and the phenotypic ratio would be 3:1 for normal:abnormal. This is because both the male and female contribute one copy of the maternal effect gene, and the outcome is determined by their combined genotypes. AA and aa individuals would have a normal or abnormal phenotype, respectively, and Aa individuals would have a normal phenotype but carry the recessive abnormal allele.