Free Punnett Square Practice Worksheet Collection - Free Printable

Punnett Square Practice Worksheet Solution

#### Part A: Vocabulary
1. Genotypes made of the same alleles
- Definition: Genotypes that have two identical alleles (e.g., AA, aa).
- Match: D. homozygous

2. Different forms of genes for a single trait
- Definition: Variants of a gene that control the same trait (e.g., tall vs. short).
- Match: A. alleles

3. Gene that is always expressed
- Definition: A dominant gene will be expressed even if only one copy is present (heterozygous or homozygous dominant).
- Match: B. dominant

4. Gene that is expressed only in the homozygous state
- Definition: A recessive gene will only be expressed when both alleles are recessive (homozygous recessive).
- Match: E. recessive

5. Genotypes made of two different alleles
- Definition: Genotypes that have one dominant and one recessive allele (e.g., Aa, Bb).
- Match: C. heterozygous

---

#### Part B: Examples of Terms
6. Homozygous dominant
- Definition: Genotypes with two identical dominant alleles (e.g., AA, TT).
- Circle: AA, KK, TT

7. Homozygous recessive
- Definition: Genotypes with two identical recessive alleles (e.g., aa, tt).
- Circle: ee, hh, ww

8. Genotypes in which dominant gene must show
- Definition: Genotypes where at least one dominant allele is present (homozygous dominant or heterozygous).
- Circle: AA, EE, RR

9. Genotypes in which recessive gene must show
- Definition: Genotypes where both alleles are recessive (homozygous recessive).
- Circle: aa, rr

---

#### Part C: Punnett Squares
10. Examine the following Punnett squares and circle those that are correct.
- First Punnett Square:
```
D d
d Dd dd
d Dd dd
```
- Correct. Each box contains the correct combination of alleles.

- Second Punnett Square:
```
D D
d Dd DD
d Dd DD
```
- Incorrect. The top row should be "D" and "D," not "D" and "d."

- Third Punnett Square:
```
A a
a AA aa
a Aa Aa
```
- Incorrect. The top row should be "A" and "a," but the combinations in the boxes are wrong.

- Fourth Punnett Square:
```
A a
a Aa aa
a Aa aa
```
- Correct. Each box contains the correct combination of alleles.

- Correct Punnett Squares:
Circle the first and fourth Punnett squares.

11. What do the letters on the outside of the Punnett square stand for?
- Answer: The letters on the outside represent the alleles of the parents. For example, if the parents are "Dd" and "dd," the alleles "D" and "d" from each parent are placed on the outside of the Punnett square.

12. What do the letters on the inside of the Punnett square stand for?
- Answer: The letters on the inside represent the genotypes of the offspring. These are formed by combining one allele from each parent.

---

#### Part D: Corn Plant Crosses
13. In corn plants, normal height (N) is dominant to short height (n). Complete these four Punnett squares showing different crosses. Then, circle all of the homozygous dominant offspring. Put an X through all the heterozygous offspring. Leave all the homozygous recessive offspring unshaded.

##### Cross 1: Nn × nn
```
N n
n NN Nn
n Nn nn
```
- Circle: None (no homozygous dominant offspring).
- X: Nn, Nn (heterozygous offspring).
- Unshaded: nn (homozygous recessive offspring).

##### Cross 2: NN × nn
```
N N
n NN NN
n NN NN
```
- Circle: NN, NN, NN, NN (all homozygous dominant offspring).
- X: None (no heterozygous offspring).
- Unshaded: None (no homozygous recessive offspring).

##### Cross 3: Nn × Nn
```
N n
N NN Nn
n Nn nn
```
- Circle: NN (homozygous dominant offspring).
- X: Nn, Nn (heterozygous offspring).
- Unshaded: nn (homozygous recessive offspring).

##### Cross 4: nn × nn
```
n n
n nn nn
n nn nn
```
- Circle: None (no homozygous dominant offspring).
- X: None (no heterozygous offspring).
- Unshaded: nn, nn, nn, nn (all homozygous recessive offspring).

---

Final Answer:

- Part A:
1. D
2. A
3. B
4. E
5. C

- Part B:
6. AA, KK, TT
7. ee, hh, ww
8. AA, EE, RR
9. aa, rr

- Part C:
10. Circle the first and fourth Punnett squares.
11. Letters on the outside represent the alleles of the parents.
12. Letters on the inside represent the genotypes of the offspring.

- Part D:
- Cross 1: Circle none; X Nn, Nn; Unshade nn.
- Cross 2: Circle NN, NN, NN, NN; X none; Unshade none.
- Cross 3: Circle NN; X Nn, Nn; Unshade nn.
- Cross 4: Circle none; X none; Unshade nn, nn, nn, nn.

Final Answer Boxed:
\boxed{
\text{See detailed explanations above.}
}