Worksheet featuring dihybrid cross problems with Punnett squares for genetics, including questions on flower color and plant height in plants, and fur color and texture in guinea pigs.

Problem Analysis

The worksheet involves setting up Punnett squares for two different scenarios and then analyzing the probabilities of specific phenotypes based on those squares. Let's solve each part step by step.

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Part 1: Dihybrid Cross for Plants (Question 1 and 2)

#### Step 1: Set up the Punnett Square
We are crossing a homozygous dominant parent (`FFDD`) with a homozygous recessive parent (`ffdd`).

- Parent 1 (FFDD):
- Genotype: `FFDD`
- Gametes: `FD` (since both alleles are dominant and homozygous)

- Parent 2 (ffdd):
- Genotype: `ffdd`
- Gametes: `fd` (since both alleles are recessive and homozygous)

Now, we set up the Punnett square:

| | Fd | Fd |
|-------|------|------|
| fD | FfDd | FfDd |
| fD | FfDd | FfDd |

#### Step 2: Analyze the Results
All offspring have the genotype `FfDd`. This means:
- All plants will have purple flowers (dominant `F`) and be tall (dominant `D`).

#### Step 3: Answer the Questions (Question 2)
Using the Punnett square:

a) Probability of producing tall plants with purple flowers?
- All offspring have the genotype `FfDd`, which results in tall plants with purple flowers.
- Probability: 100% or 1
- Possible genotype(s): `FfDd`

b) Probability of producing short plants with pink flowers?
- No offspring have the genotype `ffdd` (short and pink).
- Probability: 0%
- Possible genotype(s): None

c) Probability of producing short plants with purple flowers?
- No offspring have the genotype `Ffdd` (short and purple).
- Probability: 0%
- Possible genotype(s): None

d) Probability of producing tall plants with pink flowers?
- No offspring have the genotype `ffDd` (tall and pink).
- Probability: 0%
- Possible genotype(s): None

---

Part 2: Dihybrid Cross for Guinea Pigs (Question 3 and 4)

#### Step 1: Set up the Punnett Square
We are crossing a heterozygous parent (`BbRr`) with another heterozygous parent (`BbRr`).

- Parent 1 (BbRr):
- Genotype: `BbRr`
- Possible gametes: `BR`, `Br`, `bR`, `br`

- Parent 2 (BbRr):
- Genotype: `BbRr`
- Possible gametes: `BR`, `Br`, `bR`, `br`

Now, we set up the Punnett square:

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

#### Step 2: Analyze the Results
From the Punnett square, we can see the following genotypes and their frequencies:
- `BBRR`: 1
- `BBRr`: 2
- `BbRR`: 2
- `BbRr`: 4
- `BBrr`: 1
- `Bbrr`: 2
- `bbRR`: 1
- `bbRr`: 2
- `bbrr`: 1

#### Step 3: Determine Phenotypes
- Black fur (B\_): Dominant over white fur (bb)
- Rough fur (R\_): Dominant over smooth fur (rr)

Phenotypes:
1. Black, Rough Fur: Genotypes `BBRR`, `BBRr`, `BbRR`, `BbRr`
2. Black, Smooth Fur: Genotypes `BBrr`, `Bbrr`
3. White, Rough Fur: Genotypes `bbRR`, `bbRr`
4. White, Smooth Fur: Genotype `bbrr`

#### Step 4: Answer the Questions (Question 4)
Using the Punnett square:

a) Probability of producing guinea pigs with black, rough fur?
- Genotypes: `BBRR`, `BBRr`, `BbRR`, `BbRr`
- Total favorable outcomes: 1 + 2 + 2 + 4 = 9
- Total possible outcomes: 16
- Probability: \( \frac{9}{16} \)
- Possible genotype(s): `BBRR`, `BBRr`, `BbRR`, `BbRr`

b) Probability of producing guinea pigs with black, smooth fur?
- Genotypes: `BBrr`, `Bbrr`
- Total favorable outcomes: 1 + 2 = 3
- Total possible outcomes: 16
- Probability: \( \frac{3}{16} \)
- Possible genotype(s): `BBrr`, `Bbrr`

c) Probability of producing guinea pigs with white, rough fur?
- Genotypes: `bbRR`, `bbRr`
- Total favorable outcomes: 1 + 2 = 3
- Total possible outcomes: 16
- Probability: \( \frac{3}{16} \)
- Possible genotype(s): `bbRR`, `bbRr`

d) Probability of producing guinea pigs with white, smooth fur?
- Genotype: `bbrr`
- Total favorable outcomes: 1
- Total possible outcomes: 16
- Probability: \( \frac{1}{16} \)
- Possible genotype(s): `bbrr`

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Final Answers

#### Part 1: Plant Cross
1. Punnett Square:
```
| | Fd | Fd |
|-------|------|------|
| fD | FfDd | FfDd |
| fD | FfDd | FfDd |
```

2.
a) Probability of tall plants with purple flowers: 100%, Genotype: `FfDd`
b) Probability of short plants with pink flowers: 0%, Genotype: None
c) Probability of short plants with purple flowers: 0%, Genotype: None
d) Probability of tall plants with pink flowers: 0%, Genotype: None

#### Part 2: Guinea Pig Cross
3. Punnett Square:
```
| | 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.
a) Probability of black, rough fur: \( \frac{9}{16} \), Genotypes: `BBRR`, `BBRr`, `BbRR`, `BbRr`
b) Probability of black, smooth fur: \( \frac{3}{16} \), Genotypes: `BBrr`, `Bbrr`
c) Probability of white, rough fur: \( \frac{3}{16} \), Genotypes: `bbRR`, `bbRr`
d) Probability of white, smooth fur: \( \frac{1}{16} \), Genotype: `bbrr`

---

Boxed Final Answer

\[
\boxed{
\begin{array}{l}
\text{Part 1:} \\
\text{a) 100%, FfDd} \\
\text{b) 0%, None} \\
\text{c) 0%, None} \\
\text{d) 0%, None} \\
\\
\text{Part 2:} \\
\text{a) } \frac{9}{16}, \text{BBRR, BBRr, BbRR, BbRr} \\
\text{b) } \frac{3}{16}, \text{BBrr, Bbrr} \\
\text{c) } \frac{3}{16}, \text{bbRR, bbRr} \\
\text{d) } \frac{1}{16}, \text{bbrr}
\end{array}
}
\]