Question

In the same mouse species, a third unlinked gene (gene C/c) also has an epistatic effect on fur color. The presence of the dominant allele C (for color), allows the A/a and B/b genes to be expressed normally. The presence of two recessive alleles (cc), on the other hand, prevents any pigment from being formed, resulting in an albino (white) mouse.

Match the phenotypes on the labels at left to the genotypes listed below. Labels can be used once, more than once, or not at all.


agouti
solid color
solid color
agouti black
albino


AaBbcc
AaBBCC
Aabbcc

AAbbCc
aaBbCc
AABBcc

Answer 1

Epistasis in mice fur color involves the interaction between gene C/c and A/a, where the presence of the recessive cc genotype results in an albino phenotype, overriding the A/a genotype's influence on fur color.

Step-by-step explanation:

In the given scenario related to mouse pigmentation, the epistasis effect of gene C/c on fur color determines the phenotypes of the mice based on their genotypes. If a mouse has at least one dominant C allele, the A/a gene will influence the fur color, showing agouti or solid colors depending on whether the mouse has the AA or Aa (agouti) or aa (solid color) genotype. In contrast, having two recessive c alleles (cc) results in an albino mouse, irrespective of the A/a genotype, demonstrating the epistatic effect of gene C.

• AaBbcc - albino
• AaBBCC - solid color
• Aabbcc - albino
• AAbbCc - agouti
• aaBbCc - solid color
• AABBcc - albino

Answer 2

agouti - aaBbCc

solid color - AaBBCC

agouti black - AAbbCc

albino - AaBbcc/Aabbcc/AABBcc

Explanation: All the phenotypes that contain cc will be albinos, so they won't present any pigment deposition. Agouti black depends on the A gene to be homozygous and the B to be recessive, so the phenotype AAbbC_ is the correspondent. If A is not homozygous and B isn't recessive, we have agouti color. If B is homozygous and A recessive, we have a solid color.