This worksheet helps students practice key genetics concepts like dominant and recessive alleles through matching and Punnett square problems.

Absolutely! Let’s solve this Monohybrid Cross Practice Problems Worksheet step by step.

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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
*(e.g., AA or aa — both alleles are identical)*

2. different forms of genes for a single trait → A. alleles
*(e.g., Y and y are alleles for pea pod color)*

3. gene that is always expressed → B. dominant
*(if present, it masks the recessive allele)*

4. gene that is expressed only in the homozygous state → E. recessive
*(only shows up if no dominant allele is present — e.g., yy)*

5. genotypes made of two different alleles → C. heterozygous
*(e.g., Yy — one dominant, one recessive)*

✔ So the matching is:
> 1. D
> 2. A
> 3. B
> 4. E
> 5. C

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Circle the choices that are examples of each:

6. Dominant allele: *D, L, N, R, S*
→ Dominant alleles are represented by uppercase letters.
✔️ Circle: D, L, N, R, S

7. Recessive allele: *n, d, r, k*
→ Recessive alleles are represented by lowercase letters.
✔️ Circle: n, d, r, k

8. Homozygous dominant: *AA, KK, TT*
→ Two identical dominant alleles (both uppercase).
✔️ Circle: AA, KK, TT
*(Gg and Rr are heterozygous; mm and uu are homozygous recessive)*

9. Homozygous recessive: *ee, qq, ww*
→ Two identical recessive alleles (both lowercase).
✔️ Circle: ee, qq, ww
*(Ff, HH, Oo, Uu are not homozygous recessive — HH is homozygous dominant; others are heterozygous)*

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## ✔ Part B: Punnett Squares

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

*(Note: The actual Punnett squares aren’t shown in your image, so I can’t evaluate them. If you upload them or describe them, I’ll help! For now, I’ll skip this one.)*

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

> The alleles from each parent (gametes)
> These represent the possible alleles each parent can contribute to offspring through their gametes (sperm or egg).

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

> The possible genotypes of the offspring
> Each box shows a combination of one allele from each parent — forming the genotype of a potential offspring.

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## ✔ Problem 15: Create a Punnett Square and Give Phenotype & Genotype Ratio

> Yellow pea pods (Y) are dominant over green pods (y). A heterozygote is crossed with a homozygous dominant plant.

Step 1: Determine parental genotypes

- Heterozygote = Yy
- Homozygous dominant = YY

Step 2: Set up Punnett Square

Parent 1 (Yy) gametes: Y and y
Parent 2 (YY) gametes: Y and Y

```
| Y | Y |
--------|--------|--------|
Y | YY | YY |
--------|--------|--------|
y | Yy | Yy |
--------|--------|--------|
```

Step 3: Analyze Offspring

Genotypes:
- YY → 2 out of 4 → 50%
- Yy → 2 out of 4 → 50%

→ Genotype Ratio: 1 YY : 1 Yy
*(or 2:2 simplified to 1:1)*

Phenotypes:
- Yellow pods (Y_ ) → All offspring have at least one Y → 100% yellow
- Green pods (yy) → None

→ Phenotype Ratio: 4 yellow : 0 green → All yellow

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## 📝 Final Answers Summary:

Part A:

1. D
2. A
3. B
4. E
5. C

6. Dominant allele: D, L, N, R, S
7. Recessive allele: n, d, r, k
8. Homozygous dominant: AA, KK, TT
9. Homozygous recessive: ee, qq, ww

Part B:

12. *(Cannot answer without seeing squares)*
13. Alleles from each parent (gametes)
14. Possible genotypes of the offspring

Problem 15:

Punnett Square:
```
| Y | Y |
--------|--------|--------|
Y | YY | YY |
--------|--------|--------|
y | Yy | Yy |
--------|--------|--------|
```

Genotype Ratio: 1 YY : 1 Yy
Phenotype Ratio: 100% yellow pods (or 4:0 yellow:green)

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Let me know if you want to tackle problem #12 or any other questions — just upload or describe the Punnett squares! 😊