Question

Magical ability is a dominant trait controlled by two loci. To be able to perform magic, a person would need to carry at least on copy of the dominant allele on each of the two loci. Hermione Granger has magical ability but neither one of her parents does. Which of the following are possible genotypes for Hermione Granger’s parents?

a. AAbb x Abb
b. aaBb x AAbb
c. aaBb x aaBB
d. AaBb x AaBb
e. None of the above

Answer 1

b. aaBb x AAbb

Step-by-step explanation:

According to the information in this question, the trait for magic ability is controlled by two genes, each comprising of two alleles i.e. A,a and B,b. However, to be able to perform magic, a person would need to carry at least one copy of the dominant allele (A and B) on each of the two loci.

Hermione Granger has magical ability but neither one of her parents does. This means that although Hermione can perform magic, none of her parents can. Genetically, it means that Hermione posseses at least one copy of the dominant allele on each of the two loci i.e. her genotype is A_B_.

This is only possible in Hermione if her parents transferred a dominant allele at each loci to her. This means that the possible genotypes for Hermione Granger’s parents are aaBb (no magical ability) x AAbb (no magical ability). See the punnet square attached where the probability of producing offsprings with magical ability is 1/2 or 50%.