Question

Freckles are a dominant trait in humans; two sisters have the genotype FF for freckles. If
either sister marries a man with no freckles, what are the chances that their children will
have freckles?

Answer 1

In this scenario, both sisters have the genotype FF, which means they express the dominant trait for freckles. The man they are marrying has no freckles, which means he must have the genotype ff (homozygous recessive).

To find out the chances of their children having freckles, we can set up a simple Punnett square. Here’s how that would look:

- The possible alleles for the sisters (FF) can only contribute F (for freckles) since they do not have the recessive allele (f).
- The possible alleles for the man (ff) can only contribute f.

The Punnett square is laid out as follows:

```
F | F
---------------------
f | Ff | Ff |
---------------------
f | Ff | Ff |
```

All possible offspring combinations will be Ff, which means that all the children would have the genotype Ff.

Since the allele F is dominant over f, all children (Ff) will express freckles.

Thus, if either sister marries a man with no freckles, **100% of their children will have freckles**.