Solved Punnett Square Practice Worksheet Part A: Vocabulary ... - Free Printable

Let's go through the Punnett Square Practice Worksheet step by step and solve each part with clear explanations.

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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
→ This means both alleles are identical (e.g., AA or aa).
✔ D. homozygous

2. different forms of genes for a single trait
→ These are alternative versions of a gene (e.g., A and a).
✔ A. alleles

3. gene that is always expressed
→ This refers to a dominant allele, which masks the recessive one.
✔ B. dominant

4. gene that is expressed only in the homozygous state
→ Recessive traits are only shown when there are no dominant alleles present (i.e., aa).
✔ E. recessive

5. genotypes made of two different alleles
→ One dominant and one recessive (e.g., Aa).
✔ C. heterozygous

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Now, circle the correct examples:

#### 6. Homozygous dominant
→ Two same capital letters (both dominant).
✔ AA, KK, TT

> So circle: AA, KK, TT

#### 7. Homozygous recessive
→ Two same lowercase letters (both recessive).
✔ ee, qq, ww

> So circle: ee, qq, ww

#### 8. Genotypes in which dominant gene must show
→ Dominant trait appears if at least one dominant allele is present (A_).
So genotypes with at least one capital letter:
✔ AA, Dd, EE, Jj, RR, Ss

> Circle: AA, Dd, EE, Jj, RR, Ss

> Note: "ff" has no dominant allele → not included

#### 9. Genotypes in which recessive gene must show
→ Recessive trait only shows when no dominant allele is present → both alleles are recessive.
So only aa, rr, oo
✔ aa, rr, oo

> Circle: aa, rr, oo

> Note: Gg, Ff, Tt have dominant alleles → they don’t express recessive trait

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Part B: Punnett Squares

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

We’ll analyze each:

##### Square 1:
```
D d
d Dd dd
d Dd dd
```
- Parents: Dd × dd
- Offspring: Dd, dd, Dd, dd → 2 Dd, 2 dd → Correct
✔ Correct

##### Square 2:
```
D D
d Dd DD
d Dd DD
```
- Parents: DD × dd → should produce all Dd
- But this shows DD and Dd → Incorrect
✘ Incorrect

##### Square 3:
```
A a
A AA aa
a Aa Aa
```
- Parents: Aa × Aa
- Should be: AA, Aa, Aa, aa → but here it shows AA, aa, Aa, Aa → wait, top-left is AA, top-right is aa? That’s wrong!
- Actually, the gametes from Aa parent should give A and a.
- So:
- Top row: A and a
- Left column: A and a
- Then inside:
- A×A = AA
- A×a = Aa
- a×A = Aa
- a×a = aa
- But here it shows:
- A×A = AA → OK
- A×a = aa → ✘ Wrong! Should be Aa
- So this square is incorrect because it incorrectly combines A and a to get aa.
✘ Incorrect

##### Square 4:
```
A a
a Aa aa
a Aa aa
```
- Parents: Aa × aa
- Gametes: A, a and a, a
- Offspring: Aa, aa, Aa, aa → 2 Aa, 2 aa → Correct
✔ Correct

> So correct squares are #1 and #4

➡️ Circle Square 1 and Square 4

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

➡️ The alleles (genes) contributed by each parent (gametes)
They represent the parental gametes (sperm and egg), each carrying one allele for the trait.

✔ Answer: Gametes (or parental alleles)

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

➡️ The possible genotypes of the offspring
Each box represents a combination of one maternal and one paternal allele.

✔ Answer: Offspring genotypes

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#### 13. Complete these four Punnett squares for corn plants:

- Normal height (N) is dominant to short height (n)

We'll fill in each cross:

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Cross 1: N N × n n
Parent 1: Homozygous dominant (NN)
Parent 2: Homozygous recessive (nn)

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

All offspring: Nn → Heterozygous
→ All are normal height
→ None are homozygous dominant (no NN)
→ All are heterozygous → put X through all

> Final: All boxes have X over them (since all are heterozygous)

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Cross 2: N n × N N
Parent 1: Heterozygous (Nn)
Parent 2: Homozygous dominant (NN)

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

Offspring:
- NN → homozygous dominant → circle
- Nn → heterozygous → X through

So:
- Top-left: NN → circle
- Top-right: Nn → X
- Bottom-left: NN → circle
- Bottom-right: Nn → X

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Cross 3: N n × N n
Both parents: Heterozygous (Nn)

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

Offspring:
- NN → homozygous dominant → circle
- Nn → heterozygous → X
- nn → homozygous recessive → leave unshaded

So:
- Top-left: NN → circle
- Top-right: Nn → X
- Bottom-left: Nn → X
- Bottom-right: nn → unshaded

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Cross 4: n n × n n
Both parents: Homozygous recessive (nn)

```
n n
n nn nn
n nn nn
```

All offspring: nn → homozygous recessive → leave all unshaded

No circles, no X’s

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✔ Final Answers Summary:

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Part A: Matching

1. D. homozygous
2. A. alleles
3. B. dominant
4. E. recessive
5. C. heterozygous

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Part A: Circles

6. Homozygous dominant: AA, KK, TT
7. Homozygous recessive: ee, qq, ww
8. Dominant gene must show: AA, Dd, EE, Jj, RR, Ss
9. Recessive gene must show: aa, rr, oo

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Part B: Punnett Squares

10. Correct squares: First and fourth ones (circle them)

11. Outside letters: Parental gametes (alleles)
12. Inside letters: Offspring genotypes

13. Completed Punnett squares:

#### Cross 1: NN × nn
```
N N
n Nn Nn
n Nn Nn
```
→ All X (heterozygous)

#### Cross 2: Nn × NN
```
N n
N NN Nn
N NN Nn
```
→ Circle: NN, NN
→ X: Nn, Nn

#### Cross 3: Nn × Nn
```
N n
N NN Nn
n Nn nn
```
→ Circle: NN
→ X: Nn, Nn
→ Unshaded: nn

#### Cross 4: nn × nn
```
n n
n nn nn
n nn nn
```
→ All unshaded

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