Free Punnett Square Practice Worksheet Collection - Free Printable

Here is 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.

Answers:
1. genotypes made of the same alleles → D. homozygous
2. different forms of genes for a single trait → A. alleles
3. gene that is always expressed → B. dominant
4. gene that is expressed only in the homozygous state → E. recessive
5. genotypes made of two different alleles → C. heterozygous

✔ *Explanation:*
- Homozygous = same alleles (e.g., AA or aa)
- Alleles = different versions of a gene (e.g., A and a)
- Dominant = expressed even if only one copy is present (e.g., A_)
- Recessive = only expressed when both copies are present (e.g., aa)
- Heterozygous = two different alleles (e.g., Aa)

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Circle the choices that are examples of each:

#### 6. Homozygous dominant → AA, KK, TT
✔ *Explanation:* These have two identical dominant alleles (capital letters).

#### 7. Homozygous recessive → ee, mm, uu, qq, ww
✔ *Explanation:* These have two identical recessive alleles (lowercase letters).

#### 8. Genotypes in which dominant gene must show → AA, EE, RR, Ss, Dd, Jj
✔ *Explanation:* Any genotype with at least one dominant allele will show the dominant trait. So:
- AA, EE, RR → homozygous dominant → dominant trait
- Ss, Dd, Jj → heterozygous → still show dominant trait
*(Note: “ff” is homozygous recessive → does NOT show dominant trait)*

#### 9. Genotypes in which recessive gene must show → aa, rr, tt
✔ *Explanation:* Recessive trait is only visible when both alleles are recessive.
- Gg, Ff, Oo → heterozygous → dominant trait shows
- KK → homozygous dominant → dominant trait shows
Only aa, rr, tt will express the recessive trait.

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## Part B: Punnett Squares

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

Let’s analyze each:

Square 1:
```
D d
d Dd dd
d Dd dd
```
✔ Correct — gametes from parent 1: D, d; parent 2: d, d → offspring: Dd, dd, Dd, dd

Square 2:
```
D D
d Dd Dd
d Dd Dd
```
✔ Correct — parent 1: D, D; parent 2: d, d → all offspring Dd

Square 3:
```
A a
A AA Aa
a Aa aa
```
✔ Correct — standard heterozygous cross → AA, Aa, Aa, aa

Square 4:
```
A a
a Aa aa
a Aa aa
```
✔ Correct — parent 1: A, a; parent 2: a, a → offspring: Aa, aa, Aa, aa

🟢 ALL FOUR ARE CORRECT! → Circle all of them.

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

👉 Gametes (sex cells) from each parent.

✔ *Explanation:* The letters along the top and side represent the alleles contributed by each parent during meiosis — these combine to form offspring genotypes.

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

👉 Genotypes of the offspring.

✔ *Explanation:* Each box inside represents a possible combination of parental gametes — this is the genetic makeup (genotype) of a potential offspring.

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13. In corn plants, normal height, N, is dominant to short height, n.

Complete the four Punnett squares, then:
- Circle homozygous dominant offspring
- Put an X through heterozygous offspring
- Leave unshaded homozygous recessive offspring

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#### Square 1: Parent 1: NN × Parent 2: 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: Parent 1: Nn × Parent 2: NN
```
N n
N NN Nn
N NN Nn
```
→ Offspring: NN, Nn, NN, Nn
→ Circle the two NN (homozygous dominant)
→ X through the two Nn (heterozygous)
→ No homozygous recessive → none unshaded

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#### Square 3: Parent 1: Nn × Parent 2: Nn
```
N n
N NN Nn
n Nn nn
```
→ Offspring: NN, Nn, Nn, nn
→ Circle NN (top-left)
→ X through Nn (top-right and bottom-left)
→ Leave unshaded nn (bottom-right)

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#### Square 4: Parent 1: Nn × Parent 2: nn
```
N n
n Nn nn
n Nn nn
```
→ Offspring: Nn, nn, Nn, nn
→ No homozygous dominant → no circles
→ X through Nn (top-left and bottom-left)
→ Leave unshaded nn (top-right and bottom-right)

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## ✔ Final Summary:

Part A:

1. D
2. A
3. B
4. E
5. C
6. AA, KK, TT
7. ee, mm, uu, qq, ww
8. AA, EE, RR, Ss, Dd, Jj
9. aa, rr, tt

Part B:

10. All 4 Punnett squares are correct → circle all
11. Gametes from parents
12. Genotypes of offspring
13. See completed Punnett squares above with markings as instructed.

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Let me know if you’d like a visual version or printable answer key! 🌽🧬