Question

One parent is heterozygous for a certain trait (Dd ). The other parent is homozygous dominant (DD ) for that trait. What is the percent chance that an offspring from this cross will be heterozygous?

0%

25%

50%

100%

Answer 1

To determine the percent chance of an offspring being heterozygous from a cross between one parent that is heterozygous (Dd) and another parent that is homozygous dominant (DD), we can set up a Punnett square.

The parents are:
- Parent 1 (Dd): can contribute either D or d
- Parent 2 (DD): can only contribute D

When we fill out the Punnett square, we have:

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

The possible genotypes of the offspring are:
- 2 offspring with genotype DD
- 2 offspring with genotype Dd

So, the ratios are:
- 2 DD : 2 Dd, or simplified, 1 DD : 1 Dd.

The proportion of heterozygous (Dd) offspring is 2 out of 4, or 50%.

Therefore, the percent chance that an offspring will be heterozygous (Dd) is **50%**.