Question

A student draws a Punnett square where two parents that are heterozygous for dimples are crossed. Dimples (D) are dominant to no dimples (d).

image

Using the Punnett square, what is the percent chance that the offspring will have dimples?

A.
25%

B.
50%

C.
75%

D.
100%

Answer 1

To determine the percent chance that the offspring will have dimples when two heterozygous parents (Dd) are crossed, we can analyze the Punnett square.

The possible combinations of alleles from two heterozygous parents (D and d) can be arranged in a Punnett square as follows:

```
D d
----------------
D | DD | Dd |
----------------
d | Dd | dd |
----------------
```

From the Punnett square, the genotypes of the offspring are:
- 1 DD (homozygous dominant)
- 2 Dd (heterozygous)
- 1 dd (homozygous recessive)

Now we count the genotypes that will have dimples (either DD or Dd):
- DD: 1
- Dd: 2

Total offspring with dimples (dimples = D allele):
- 1 (DD) + 2 (Dd) = 3

Total offspring represented:
- 4 (1 DD + 2 Dd + 1 dd)

Now, we calculate the percentage chance that an offspring will have dimples:
\[ \text{Chance of dimples} = \frac{\text{Number of offspring with dimples}}{\text{Total number of offspring}} \times 100 \]
\[ \text{Chance of dimples} = \frac{3}{4} \times 100 = 75\% \]

Thus, the percent chance that the offspring will have dimples is:

**C. 75%**