Dihybrid cross worksheet with Punnett squares for genetics problems involving tall vs. dwarf plants and purple vs. white flowers, and black vs. white fur and rough vs. smooth fur in guinea pigs.

Problem Overview:

The worksheet involves setting up Punnett squares for two different dihybrid crosses and calculating probabilities of specific phenotypes. Let's solve each part step by step.

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Question 1: Setting up the Punnett Square

#### Given Information:
- Dominant allele for tall plants = D
- Recessive allele for dwarf plants = d
- Dominant allele for purple flowers = W
- Recessive allele for white flowers = w
- Cross a homozygous dominant parent (DDWW) with a homozygous recessive parent (ddww).

#### Step 1: Determine the Genotypes of the Parents
- Parent 1 (homozygous dominant): DDWW
- Parent 2 (homozygous recessive): ddww

#### Step 2: Determine the Gametes
- Parent 1 (DDWW) produces gametes: DW
- Parent 2 (ddww) produces gametes: dw

#### Step 3: Set Up the Punnett Square
The Punnett square will have DW as the row headers and dw as the column headers.

| | DW | DW |
|-------|----------|----------|
| dw| DdWw | DdWw |
| dw| DdWw | DdWw |

#### Result:
All offspring will have the genotype DdWw.

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Question 2: Calculating Probabilities Using the Punnett Square

#### Part (a): Probability of producing tall plants with purple flowers
- Tall plants require at least one D allele (D_).
- Purple flowers require at least one W allele (W_).
- All offspring have the genotype DdWw, which means they are tall and have purple flowers.
- Probability: 100% or 1.0

#### Part (b): Probability of producing dwarf plants with white flowers
- Dwarf plants require the genotype dd.
- White flowers require the genotype ww.
- None of the offspring have the genotype ddww.
- Probability: 0%

#### Part (c): Probability of producing tall plants with white flowers
- Tall plants require at least one D allele (D_).
- White flowers require the genotype ww.
- None of the offspring have the genotype D_ww.
- Probability: 0%

#### Part (d): Probability of producing dwarf plants with purple flowers
- Dwarf plants require the genotype dd.
- Purple flowers require at least one W allele (W_).
- None of the offspring have the genotype ddW_.
- Probability: 0%

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Question 3: Setting up the Punnett Square

#### Given Information:
- Dominant allele for black fur in guinea pigs = B
- Recessive allele for white fur in guinea pigs = b
- Dominant allele for rough fur in guinea pigs = R
- Recessive allele for smooth fur in guinea pigs = r
- Cross a heterozygous parent (BbRr) with a heterozygous parent (BbRr).

#### Step 1: Determine the Genotypes of the Parents
- Both parents are heterozygous: BbRr

#### Step 2: Determine the Gametes
Each parent can produce the following gametes:
- BR, Br, bR, br

#### Step 3: Set Up the Punnett Square
The Punnett square will have BR, Br, bR, br as both row and column headers.

| | BR | Br | bR | br |
|-------|----------|----------|----------|----------|
| BR| BBRR | BBRr | BbRR | BbRr |
| Br| BBRr | BBrr | BbRr | Bbrr |
| bR| BbRR | BbRr | bbRR | bbRr |
| br| BbRr | Bbrr | bbRr | bbrr |

#### Result:
The Punnett square shows all possible genotypes of the offspring.

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Question 4: Calculating Probabilities Using the Punnett Square

#### Part (a): Probability of producing guinea pigs with black, rough fur
- Black fur requires at least one B allele (B_).
- Rough fur requires at least one R allele (R_).
- Offspring with black, rough fur include:
- BBRR, BBRr, BbRR, BbRr
- Count the number of such offspring: 9 out of 16.
- Probability: \( \frac{9}{16} \) or approximately 56.25%.

#### Part (b): Probability of producing guinea pigs with black, smooth fur
- Black fur requires at least one B allele (B_).
- Smooth fur requires the genotype rr.
- Offspring with black, smooth fur include:
- BBrr, Bbrr
- Count the number of such offspring: 3 out of 16.
- Probability: \( \frac{3}{16} \) or approximately 18.75%.

#### Part (c): Probability of producing guinea pigs with white, rough fur
- White fur requires the genotype bb.
- Rough fur requires at least one R allele (R_).
- Offspring with white, rough fur include:
- bbRR, bbRr
- Count the number of such offspring: 3 out of 16.
- Probability: \( \frac{3}{16} \) or approximately 18.75%.

#### Part (d): Probability of producing guinea pigs with white, smooth fur
- White fur requires the genotype bb.
- Smooth fur requires the genotype rr.
- Offspring with white, smooth fur include:
- bbrr
- Count the number of such offspring: 1 out of 16.
- Probability: \( \frac{1}{16} \) or approximately 6.25%.

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Final Answers:

1. Punnett Square for Question 1:
```
| | DW | DW |
|-------|-------|-------|
| dw | DdWw | DdWw |
| dw | DdWw | DdWw |
```

2. Probabilities for Question 2:
- (a) 100%
- (b) 0%
- (c) 0%
- (d) 0%

3. Punnett Square for Question 3:
```
| | BR | Br | bR | br |
|-------|-------|-------|-------|-------|
| BR | BBRR | BBRr | BbRR | BbRr |
| Br | BBRr | BBrr | BbRr | Bbrr |
| bR | BbRR | BbRr | bbRR | bbRr |
| br | BbRr | Bbrr | bbRr | bbrr |
```

4. Probabilities for Question 4:
- (a) \( \frac{9}{16} \)
- (b) \( \frac{3}{16} \)
- (c) \( \frac{3}{16} \)
- (d) \( \frac{1}{16} \)

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Boxed Final Answer:

\[
\boxed{
\begin{array}{l}
\text{Question 2:} \\
\text{(a) } 100\% \\
\text{(b) } 0\% \\
\text{(c) } 0\% \\
\text{(d) } 0\% \\
\\
\text{Question 4:} \\
\text{(a) } \frac{9}{16} \\
\text{(b) } \frac{3}{16} \\
\text{(c) } \frac{3}{16} \\
\text{(d) } \frac{1}{16}
\end{array}
}
\]