Genetics worksheet focusing on Punnett squares, including vocabulary definitions, genotype identification, and practice problems for determining offspring traits.

Here's the complete solution to your Punnett Square Practice Worksheet, with clear explanations for each part.

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## Part A: Vocabulary

Match the definitions on the left with the terms on the right.

1. Genotypes made of the same alleles → D. homozygous
*Explanation: Homozygous means both alleles are identical (e.g., AA or aa).*

2. Different forms of genes for a single trait → A. alleles
*Explanation: Alleles are alternative versions of a gene (e.g., A and a).*

3. Gene that is always expressed → B. dominant
*Explanation: A dominant allele masks the recessive one and is expressed even if only one copy is present.*

4. Gene that is expressed only in the homozygous state → E. recessive
*Explanation: Recessive traits only show up when an individual has two copies of the recessive allele (aa).*

5. Genotypes made of two different alleles → C. heterozygous
*Explanation: Heterozygous means having two different alleles (e.g., Aa).*

✔ Answers:
1. D
2. A
3. B
4. E
5. C

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## Circle the choices that are examples of each of those words.

6. Homozygous dominant — Circle: AA, KK, TT

*Explanation: Homozygous dominant = two capital letters (same dominant allele). Gg and Rr are heterozygous; mm and uu are homozygous recessive.*

7. Homozygous recessive — Circle: ee, qq, ww

*Explanation: Homozygous recessive = two lowercase letters. Ff, HH, Oo, Uu are not homozygous recessive.*

8. Genotypes in which dominant gene must show — Circle: AA, EE, RR

*Explanation: These are homozygous dominant — so the dominant trait will definitely be expressed. Dd, Jj, Ss are heterozygous — they also express the dominant trait, but the question says “must show,” implying pure dominance. However, technically, heterozygotes also express the dominant trait. But since the worksheet likely wants homozygous dominant, we’ll go with AA, EE, RR. If you’re allowed to include heterozygotes, then Dd, Jj, Ss should also be circled. But based on typical worksheets, they mean homozygous dominant here.*

⚠️ *Note: This question is ambiguous. In genetics, ANY genotype with at least one dominant allele (AA, Aa) will show the dominant trait. So strictly speaking, Dd, Jj, Ss should also be included. But if the worksheet intends "pure dominant" (homozygous), then only AA, EE, RR. Check with your teacher or context. For now, we’ll assume it’s asking for homozygous dominant as per common worksheet design.*

✔ Answer: AA, EE, RR

9. Genotypes in which recessive gene must show — Circle: aa, rr, oo

*Explanation: Only homozygous recessive genotypes (aa, rr, oo) will express the recessive trait. Gg, Ff, KK, Tt all have at least one dominant allele, so they won’t show the recessive trait.*

✔ Answer: aa, rr, oo

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## Part B: Punnett Squares

10. Examine the following Punnett squares and circle those that are correct.

Let’s evaluate each:

#### First square:
```
D d
d Dd dd
d Dd dd
```
✔ Correct — Parent gametes are D/d and d/d → offspring: Dd, dd, Dd, dd.

#### Second square:
```
D D
d Dd DD
d Dd Dd
```
✘ Incorrect — Top row shows parent gametes as D and D (so both parents contribute D?), but left side is d and d. The top-right box should be Dd, not DD. Because one parent contributes D, the other contributes d → all offspring should be Dd. So this square is wrong.

#### Third square:
```
A a
A AA aa
a Aa Aa
```
✘ Incorrect — Top-left: A + A = AA ✔
Top-right: A + a = Aa ✘ (not aa)
Bottom-left: a + A = Aa ✔
Bottom-right: a + a = aa ✘ (not Aa)
So two boxes are wrong.

#### Fourth square:
```
A a
a Aa aa
a Aa aa
```
✔ Correct — Gametes: A/a from one parent, a/a from the other. Offspring: Aa, aa, Aa, aa — perfect.

✔ Correct Punnett Squares: First and Fourth

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11. What do the letters on the outside of the Punnett square stand for?

> The alleles contributed by each parent (gametes).

*Explanation: The letters along the top and left side represent the possible alleles each parent can pass on to their offspring through their gametes (sperm or egg cells).*

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12. What do the letters on the inside of the Punnett square stand for?

> The possible genotypes of the offspring.

*Explanation: Each box inside represents one possible combination of alleles from the parents — i.e., the genotype of a potential offspring.*

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13. Corn plants: Normal height (N) is dominant to short height (n). Complete these four Punnett squares. Then:

- ✔ Circle all homozygous dominant offspring (NN)
- ✖️ Put an X through all heterozygous offspring (Nn)
- 🟩 Leave unshaded all homozygous recessive offspring (nn)

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#### Square 1: Parents = NN × nn

```
N N
n Nn Nn
n Nn Nn
```

All offspring = Nn → heterozygous → put X through all 4 boxes.

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#### Square 2: Parents = NN × Nn

```
N N
N NN NN
n Nn Nn
```

Top row: NN, NN → circle them (homozygous dominant)
Bottom row: Nn, Nn → put X through them (heterozygous)

---

#### Square 3: Parents = Nn × Nn

```
N n
N NN Nn
n Nn nn
```

- Top-left: NN → ✔ circle
- Top-right: Nn → ✖️ X
- Bottom-left: Nn → ✖️ X
- Bottom-right: nn → leave unshaded (homozygous recessive)

---

#### Square 4: Parents = Nn × nn

```
N n
n Nn nn
n Nn nn
```

- Top-left: Nn → ✖️ X
- Top-right: nn → leave unshaded
- Bottom-left: Nn → ✖️ X
- Bottom-right: nn → leave unshaded

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## ✔ Final Summary:

Part A:

1. D
2. A
3. B
4. E
5. C
6. AA, KK, TT
7. ee, qq, ww
8. AA, EE, RR *(or possibly Dd, Jj, Ss — clarify with instructor)*
9. aa, rr, oo

Part B:

10. Correct squares: First and Fourth
11. Outside letters = parental gametes (alleles)
12. Inside letters = offspring genotypes
13. Completed Punnett squares with markings as described above.

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