Solved Monohybrid Cross Practice Some ideas refreshed: . | Chegg.com - Free Printable

Problem Analysis:

The worksheet involves solving monohybrid crosses for incomplete dominance in flowers and human traits. Here's a breakdown of the tasks:

#### Part 3: Incomplete Dominance
1. Cross a red flower with a white flower
- Red flowers are dominant over white flowers.
- Heterozygous individuals (pink flowers) exhibit incomplete dominance.

2. Cross 2 pink flowers
- Pink flowers are heterozygous.

3. Cross a white flower with a pink flower
- White flowers are recessive.

4. Cross a red flower with a pink flower
- Red flowers are dominant.

#### Part 4: Human Traits and Test Crosses
- Focus on eye color in humans, where brown eyes are dominant over blue eyes.
- Determine genotypes and probabilities based on given scenarios.

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Solution:

#### Part 3: Incomplete Dominance

##### 1. Cross a red flower with a white flower
- Genotypes:
- Red flower: \( RR \) (homozygous dominant)
- White flower: \( rr \) (homozygous recessive)

- Punnett Square:
```
R r
R RR Rr
r Rr rr
```

- a. Genotype probabilities:
- \( RR \): 25%
- \( Rr \): 50%
- \( rr \): 25%

- b. Phenotype probabilities:
- Red (\( RR \) or \( Rr \)): 75%
- White (\( rr \)): 25%

---

##### 2. Cross 2 pink flowers
- Genotypes:
- Pink flower: \( Rr \) (heterozygous)

- Punnett Square:
```
R r
R RR Rr
r Rr rr
```

- a. Genotype probabilities:
- \( RR \): 25%
- \( Rr \): 50%
- \( rr \): 25%

- b. Phenotype probabilities:
- Red (\( RR \)): 25%
- Pink (\( Rr \)): 50%
- White (\( rr \)): 25%

---

##### 3. Cross a white flower with a pink flower
- Genotypes:
- White flower: \( rr \)
- Pink flower: \( Rr \)

- Punnett Square:
```
R r
r Rr rr
r Rr rr
```

- a. Genotype probabilities:
- \( Rr \): 50%
- \( rr \): 50%

- b. Phenotype probabilities:
- Pink (\( Rr \)): 50%
- White (\( rr \)): 50%

---

##### 4. Cross a red flower with a pink flower
- Genotypes:
- Red flower: \( RR \)
- Pink flower: \( Rr \)

- Punnett Square:
```
R r
R RR RR
R RR Rr
```

- a. Genotype probabilities:
- \( RR \): 50%
- \( Rr \): 50%

- b. Phenotype probabilities:
- Red (\( RR \) or \( Rr \)): 100%
- No white flowers

---

#### Part 4: Human Traits and Test Crosses

##### 1. If Kevin has blue eyes, but both of his parents have brown eyes, what must their genotypes be?
- Dominant trait: Brown eyes (\( B \))
- Recessive trait: Blue eyes (\( b \))

- Kevin has blue eyes (\( bb \)), so he received one \( b \) allele from each parent.
- Both parents have brown eyes (\( BB \) or \( Bb \)). Since they passed on \( b \) alleles to Kevin, they must both be heterozygous (\( Bb \)).

- Answer: Both parents must have the genotype \( Bb \).

##### 2. What is the probability that Kevin could have a brown-eyed sibling?
- Parents' genotypes: \( Bb \times Bb \)

- Punnett Square:
```
B b
B BB Bb
b Bb bb
```

- Phenotype probabilities:
- Brown eyes (\( BB \) or \( Bb \)): 75%
- Blue eyes (\( bb \)): 25%

- Probability of a brown-eyed sibling: 75%

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Final Answers:

1. Cross a red flower with a white flower:
- Genotype probabilities: \( RR = 25\%, Rr = 50\%, rr = 25\% \)
- Phenotype probabilities: Red = 75%, White = 25%

2. Cross 2 pink flowers:
- Genotype probabilities: \( RR = 25\%, Rr = 50\%, rr = 25\% \)
- Phenotype probabilities: Red = 25%, Pink = 50%, White = 25%

3. Cross a white flower with a pink flower:
- Genotype probabilities: \( Rr = 50\%, rr = 50\% \)
- Phenotype probabilities: Pink = 50%, White = 50%

4. Cross a red flower with a pink flower:
- Genotype probabilities: \( RR = 50\%, Rr = 50\% \)
- Phenotype probabilities: Red = 100%

5. Kevin's parents' genotypes: \( Bb \times Bb \)

6. Probability of a brown-eyed sibling: \( \boxed{75\%} \)

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This completes the solution. Let me know if you need further clarification!