Question

Fruit flies can either have a brown body or a black body. The allele for a brown body (B) is dominant to the allele for a black body (b).

A brown fruit fly was crossed with a black fruit fly as shown below. What is the probability of a resulting offspring being brown?
B B
b ? ?
b ? ?
A.
100%
B.
25%
C.
50%
D.
75%

Answer 1

A. 100%

Explanation: The brown parent is BB (gives B and B), the black parent is bb (gives b and b). All four Punnett-square boxes are Bb, which show the brown phenotype because B is dominant.