A student learns that the traits offspring express depend on the genes they receive from their parents during melosis.

Question

She knows that brown eyes (B) are dominant to blue eyes (b). She views a Punnett square of a cross between a homozygous parent and a heterozygous parent.
B b
B BB Bb
B BB Bb

Which TWO questions can the student answer using the Punnett square?
A. What is the genotype of the female parent?
B. What are the genotypes of the grandparents?
C. What is the probability of an offspring being male?
D. What is the probability of an offspring carrying a recessive allele?
E. What is the percent likelihood of an offspring having brown eyes?

Answer 1

Based on the given Punnett square and information about eye color genetics, the student can answer the following two questions:

A. What is the genotype of the female parent?

• The Punnett square indicates that one parent is homozygous (BB), and because it is a square depicting a cross between a homozygous (BB) and a heterozygous (Bb) parent, you can determine that the female parent (homozygous) must have the genotype BB.

E. What is the percent likelihood of an offspring having brown eyes?

• From the Punnett square, there are four potential offspring genotypes: 2 BB (homozygous brown) and 2 Bb (heterozygous brown). Therefore, 100% (2 BB + 2 Bb = 4) of the offspring will have the brown eye trait.

The student cannot answer questions B, C, or D using the information from the provided Punnett square. Thus, the answers are A and E.