Genetics worksheet with Punnett square exercises on dog fur color inheritance.

Let’s solve problem #5 step by step.

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Problem 5:
> The female dog is heterozygous. The male dog is heterozygous. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.

First, let’s understand what “heterozygous” means.

In genetics, when we talk about fur color in dogs (like in problem #4), we usually assume:
- F = dominant allele → black fur
- f = recessive allele → grey fur

“Heterozygous” means the dog has one of each allele → Ff

So both parents are Ff.

Now, let’s set up the Punnett Square.

We write the female’s alleles on top: F and f
We write the male’s alleles on the side: F and f

The square looks like this:

```
Female
F f
+-----+-----+
Male F| FF | Ff |
+-----+-----+
f| Ff | ff |
+-----+-----+
```

Now fill in the boxes:

- Top-left: F (from mom) + F (from dad) = FF
- Top-right: f (from mom) + F (from dad) = Ff
- Bottom-left: F (from mom) + f (from dad) = Ff
- Bottom-right: f (from mom) + f (from dad) = ff

So the four possible puppy genotypes are:
→ FF, Ff, Ff, ff

That means:
- FF: 1 out of 4 → 25%
- Ff: 2 out of 4 → 50%
- ff: 1 out of 4 → 25%

Now for phenotypes (what they look like):

Remember:
- FF and Ff → black fur (because F is dominant)
- ff → grey fur (only if no dominant F)

So:
- Black fur: FF + Ff + Ff = 3 out of 4 → 75%
- Grey fur: ff = 1 out of 4 → 25%

Double-checking:
Genotypes: 25% FF, 50% Ff, 25% ff → adds to 100% ✔
Phenotypes: 75% black, 25% grey → adds to 100% ✔

Everything checks out!

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Final Answer:
% of possible Genotypes:
FF: 25%
Ff: 50%
ff: 25%

% of possible Phenotypes:
Black fur: 75%
Grey fur: 25%