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 ? ?
The Punnett square for this cross would be:
| B | b |
--|-----|-----|
b | Bb | bb |
--|-----|-----|
b | Bb | bb |
Therefore, there is a 50% chance of the resulting offspring being brown (Bb) and a 50% chance of the offspring being black (bb).