Question

Zuzu is a white cat. She is genotype Ww for the "white masking gene" that reduces the number of melanocytes (pigment-containing cells). As a result, her body makes pigment, but it cannot get into the cells where it would color the fur. Zuzu's white masking gene is _____ to the melanin pigment gene because it prevents full expression of the pigment.

a) Recessive
b) Dominant
c) Co-dominant
d) Incomplete dominant

Answer 1

Zuzu's white masking gene is dominant over the melanin pigment gene, explained by the concept of epistasis, which is when one gene masks or suppresses the expression of another gene.

Step-by-step explanation:

The white masking gene that Zuzu exhibits can be understood through the concept of epistasis, where one gene interferes with the expression of another gene. In the provided example regarding mice fur color, the presence of the recessive c allele results in an albino mouse, regardless of the alleles for the agouti gene. This is because the C gene is necessary for pigment production.

In Zuzu's case, the white masking gene is dominant over the gene responsible for melanin pigment production, as it prevents the pigment from coloring the fur even though the pigment is made. Therefore, Zuzu's white masking gene is dominant to the melanin pigment gene because it prevents full expression of the pigment.