Question

If Greg's mother has a cleft chin (genotype Bb) and his father does not (genotype bb), what are the chances that Greg has a cleft chin?

25%
50%
75%
100%

Answer 1

To determine the chances that Greg has a cleft chin, we need to analyze the genotypes of his parents.

- Greg’s mother has a cleft chin, which means she has the genotype Bb (where "B" represents the dominant allele for a cleft chin and "b" represents the recessive allele).
- Greg’s father does not have a cleft chin, so his genotype is bb.

When we set up a Punnett square to determine the possible genotypes of their offspring, we get:

```
B | b
------------
b | Bb | bb
------------
b | Bb | bb
```

From this Punnett square, we see the possible genotypes for Greg:

- Bb (which means he will have a cleft chin)
- bb (which means he will not have a cleft chin)

The probabilities of obtaining these genotypes are:
- Bb = 2 out of 4 (or 50%)
- bb = 2 out of 4 (or 50%)

Therefore, the chance that Greg has a cleft chin (genotype Bb) is **50%**.