Dihybrid Cross Problem Set

Problem 13: AaBb dihybrid cross involving epistasis


Two unlinked loci effect mouse hair color. AA or Aa mice are agouti. Mice with genotype aa are albino because all pigment production is blocked, regardless of the phenotype at the second locus. At the second locus, the B allele (agouti coat) is dominant to the b allele (black coat). What would be the result of a cross between two agouti mice of genotype AaBb?

A. 4 agouti: 4 black: 8 albino
B. 9 agouti: 3 black: 3 albino: 1 grey
C. 9 agouti: 3 black: 4 albino
This is a variant of the normal 9:3:3:1 ratio for a normal dihybrid cross without epistasis.
D. 8 agouti: 4 black: 4 albino

The Biology Project
University of Arizona
Monday, October 13, 1997
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