Name ________________________________________ Date __________ Period ________
Worksheet: Monohybrid Crosses
U N I T 3 : G E N E T I C S
Directions: Answer the following genetic cross problems. You can refer to the “Punnett
Square Cheat Sheet” attached at the end of this worksheet to help you solve the different types
of problems. It is essential that you know the all of the vocabulary inlcuded in the “cheat sheet”
as well. Remember when you are doing a genetic cross to follow the steps below to complete!
STEP 1: Determine what kind of problem you are trying to solve.
STEP 2: Determine letters you will use to specify traits.
STEP 3: Determine parent’s genotypes.
STEP 4: Make your punnett square and make gametes
STEP 5: Complete cross and determine possible offspring.
STEP 6: Determine genotypic and phenotypic ratios.
Single-Factor Crosses (Mono-hybrid)
1. In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene,
and normal hearing is due to its dominant allele (D). What percentage of the offspring of
a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal
hearing? A homozygous deaf dog and a homozygous normal?
2. In man, normal pigmentation is due to a dominant allele (C), and albinism to it’s recessive
allele (c). A normal man marries an albino woman. Their first child is albino. What are
the genotypes of these three people? If there are more children, what would they
probably be like?
3. In minks, brown is dominant over silver-blue color. What offspring would you predict if
you crossed a homozygous brown mink with a silver-blue mink?
