Worksheet on incomplete dominance and co-dominance with solved genetics problems and Punnett squares.

You’ve uploaded a worksheet titled “Incomplete Dominance and Co-Dominance Practice Problems”, and it appears you want me to solve and explain each problem — even though the worksheet already has answers filled in (likely by a student or teacher). I’ll go through each question, verify the correctness, and provide clear explanations so you understand the genetics behind incomplete dominance.

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## 🔹 Key Concept: Incomplete Dominance
In incomplete dominance, neither allele is completely dominant. The heterozygous genotype produces a blended or intermediate phenotype.

Example: Red flower (RR) × White flower (WW) → Pink flower (RW)

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# ✔ Problem 1: Mice Coat Color

> Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while cream-colored mice are heterozygous. If two cream-colored mice mate, what phenotypic ratio can we expect of their offspring? Show the Punnett Square.

🧬 Genotypes:

- Yellow = YY
- White = WW
- Cream = YW (heterozygous)

👨‍👩‍👧‍👦 Cross: Cream × Cream → YW × YW

📊 Punnett Square:

```
| Y | W
-----|------|-----
Y | YY | YW
W | YW | WW
```

🧪 Offspring:

- YY → Yellow → 1/4
- YW → Cream → 2/4
- WW → White → 1/4

✔ Phenotypic Ratio: 1 Yellow : 2 Cream : 1 White → 1:2:1

✔️ Answer Correct!

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# ✔ Problem 2: Radishes (Red × White → Purple F1, then F1 self-pollinates)

> In radishes, red and white are pure-breeding colors, while hybrids are purple. If a red radish is crossed with a white radish, what will be the phenotype of the F2 generation (assuming the F1 generation self-pollinates)? Show the Punnett Square.

🧬 Genotypes:

- Red = RR
- White = WW
- Purple = RW (incomplete dominance)

Step 1: P Generation → RR × WW

All F1 offspring = RW (Purple)

Step 2: F1 Self-Pollination → RW × RW

📊 Punnett Square:

```
| R | W
-----|------|-----
R | RR | RW
W | RW | WW
```

🧪 Offspring:

- RR → Red → 1/4 → 25%
- RW → Purple → 2/4 → 50%
- WW → White → 1/4 → 25%

✔ Phenotypic Ratio: 1 Red : 2 Purple : 1 White

✔️ Answer Correct!

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# ✔ Problem 3: Snapdragon Flower Color

> In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (W). The heterozygous genotype is expressed as pink.

a) Phenotype of RR? → Red

b) Phenotype of WW? → White

c) Phenotype of RW? → Pink

✔️ All correct — standard incomplete dominance pattern.

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# ✔ Problem 4: Pink × White Snapdragon

> A pink-flowered plant is crossed with a white-flowered plant. Show the Punnett Square. What is the probability of producing a pink-flowered plant?

🧬 Genotypes:

- Pink = RW
- White = WW

📊 Punnett Square:

```
| R | W
-----|------|-----
W | RW | WW
W | RW | WW
```

🧪 Offspring:

- RW → Pink → 2/4 → 50%
- WW → White → 2/4 → 50%

✔ Probability of pink = 50%

✔️ Answer Correct!

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# ✔ Problem 5: Which cross produces the MOST pink-flowered plants?

> What cross will produce the most pink-flowered plants? Show a punnett square to support your answer.

💡 Best cross: RR × WW

→ All offspring = RW (Pink) → 100% pink

📊 Punnett Square:

```
| R | R
-----|------|-----
W | RW | RW
W | RW | RW
```

✔ All 4 offspring = RW → Pink

✔️ Answer Correct! (RR × WW gives 100% pink)

> *Note: Any cross involving one RR and one WW parent will give 100% pink. Other crosses like RW × RW give only 50% pink.*

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# ✔ Problem 6: Andalusian Fowls (Black × White → Bluish-gray)

> In Andalusian fowls, black individuals (B) and white individuals (W) are homozygous. A homozygous black bird is crossed with a homozygous white bird. The offspring are all bluish-gray. Show the cross...

🧬 Genotypes:

- Black = BB
- White = WW
- Bluish-gray = BW (incomplete dominance)

👨‍👩‍👧‍👦 Cross: BB × WW

📊 Punnett Square:

```
| B | B
-----|------|-----
W | BW | BW
W | BW | BW
```

🧪 Offspring: All BW → Bluish-gray

✔ Parents: BB (black) × WW (white)
✔ Offspring: BW (gray)

✔️ Answer Correct!

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# ✔ Problem 7: Black × Bluish-gray Cross

> What are the genotypic and phenotypic ratios if a black individual is crossed with a bluish-gray individual? Show the Punnett Square.

🧬 Genotypes:

- Black = BB
- Bluish-gray = BW

👨‍👩‍👧‍👦 Cross: BB × BW

📊 Punnett Square:

```
| B | B
-----|------|-----
B | BB | BB
W | BW | BW
```

🧪 Offspring:

- BB → Black → 2/4 → 50%
- BW → Bluish-gray → 2/4 → 50%

✔ Genotypic Ratio: 2 BB : 2 BW → Simplified: 1:1

But worksheet says “2:2:0” — technically correct if listing BB : BW : WW (but WW = 0)

So:
→ Genotype: 2 BB : 2 BW : 0 WW → 2:2:0
→ Phenotype: 2 Black : 2 Gray : 0 White → 2:2:0

✔️ Answer is technically acceptable, though usually we simplify ratios (e.g., 1:1 for both genotype and phenotype).

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## 🎯 Final Summary:

All answers on the worksheet are correct and follow the rules of incomplete dominance.

🔹 Incomplete dominance = blending phenotype in heterozygotes
🔹 Punnett squares show 1:2:1 phenotypic ratios in F2 when crossing two heterozygotes
🔹 Crossing homozygous dominant × homozygous recessive gives 100% heterozygous (intermediate phenotype)

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## 💡 Tip for Students:
When solving these problems:
1. Assign letters to alleles (e.g., R = red, W = white).
2. Remember: Homozygous = purebred, Heterozygous = blended phenotype.
3. Always draw the Punnett square — it prevents mistakes!
4. Phenotypic ratios are based on observable traits, not genotypes.

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✔ You’re all set! This worksheet demonstrates a solid understanding of incomplete dominance. Great job! 🌟