Dimples and DNA
In humans, dimpled cheeks are a dominant trait, DD or Dd. Nondimpled cheeks are a recessive trait, dd.
1. Imagine that Parent A, with the genotype DD, has dimpled cheeks. Parent B has the genotype dd
and has nondimpled cheeks. The Punnett square below diagrams the cross between Parent A and
Parent B. Complete the Punnett square. (The first square has been done for you.)
2. A Punnett square shows what genotypes are possible for the offspring of a certain cross. What
genotypes are possible for the offspring of the parents above?
3. Each of the four squares of a Punnett square represents 25% probability that the offspring will have
that genotype. What is the probability that the offspring for these parents have dimpled cheeks?
Patent X, with the genotype Dd, has dimpled cheeks. Parent Y also has the genotype Dd and has
dimpled cheeks. Complete the Punnett square below to determine their possible offspring.
4. What is the probability that the offspring for these parents will have the following genotypes?
Genotype
%
DD
Dd
dd
5. What is the probability that the offspring for these parents will have nondimpled cheeks?
6. What is the probability that the offspring for these parents will have dimpled cheeks?
