1. No category

Biology 30
Name: _______________________
Worksheet #6: Epistasis Practice
1. In man, the gene D is necessary for normal ear cochlea and gene E is necessary for a normal
auditory nerve. In the absence of either of these factors, the individual is deaf (that is ee or
dd make you deaf). Do the following crosses and give the phenotypic ratios for deafness.
a. DDee x DdEe
b. DdEe x DdEe
c. DDee x ddEE
Biology 30
Name: _______________________
2. Eye color in humans: At least two pairs of genes control eye color. Both pairs influence the
production of the pigment, melanin, but act independently. One pair of alleles is B (Brown
color; dominant) and b (blue color); the other pair is A (pigment production; dominant)
and a (no pigment production; albino). The gene pair aa is epistatic to (masks) B and b and
produces the nonpigmented eyes of the albino.
a. Give the genotypes and phenotypes of the possible offspring of the mating
bbAa x Bbaa and indicate the parents phenotypes.
3. Color in the yellow daisy: the color of the center of a yellow daisy is controlled by two pairs
of genes, A, a and B, b. Each pair acts independently of the other: aa is epistatic to B and b
and bb is epistatic to A and a. The presences of aa or bb (or both) produces a yellowcentered flower; all other combinations produce a purple-centered flower.
a. Give the genotypes and phenotypes of the possible offspring of the mating
aaBb x AaBb and indicate the parents phenotypes.