Dihybrid Cross Worksheet Answers Beautiful Chapter 10 Dihybrid ... - Free Printable

Problem Analysis:

The worksheet involves solving dihybrid crosses in rabbits, where two traits are being considered: hair color and eye color. The genotypes for these traits are given as follows:

- Hair Color:
- Dominant allele: G (gray hair)
- Recessive allele: g (white hair)

- Eye Color:
- Dominant allele: B (black eyes)
- Recessive allele: b (red eyes)

We need to determine the phenotypes of specific genotypes and perform dihybrid crosses to find the proportions of offspring with different phenotypes.

---

Step 1: Determine the Phenotypes of Given Genotypes

#### Question 1:
We are asked to identify the phenotypes of rabbits with the following genotypes:
1. GgbB
2. ggBB
3. ggbB
4. GgBB

#### Solution:
- GgbB:
- Hair color: Gg → Gray hair (dominant G is present)
- Eye color: Bb → Black eyes (dominant B is present)
- Phenotype: Gray hair, black eyes

- ggBB:
- Hair color: gg → White hair (recessive g is homozygous)
- Eye color: BB → Black eyes (dominant B is homozygous)
- Phenotype: White hair, black eyes

- ggbB:
- Hair color: gg → White hair (recessive g is homozygous)
- Eye color: Bb → Black eyes (dominant B is present)
- Phenotype: White hair, black eyes

- GgBB:
- Hair color: Gg → Gray hair (dominant G is present)
- Eye color: BB → Black eyes (dominant B is homozygous)
- Phenotype: Gray hair, black eyes

#### Final Answer for Question 1:
\[
\boxed{
\begin{aligned}
&\text{GgbB: Gray hair, black eyes} \\
&\text{ggBB: White hair, black eyes} \\
&\text{ggbB: White hair, black eyes} \\
&\text{GgBB: Gray hair, black eyes}
\end{aligned}
}
\]

---

Step 2: Perform Dihybrid Crosses

#### Question 2:
A male rabbit with genotype GGbb is crossed with a female rabbit with genotype ggBB. We need to fill out the Punnett square and determine the phenotypes and proportions of the offspring.

#### Solution:
1. Identify the gametes produced by each parent:
- Male (GGbb):
- All gametes will be Gb (since G and b are linked in this genotype).
- Female (ggBB):
- All gametes will be gB (since g and B are linked in this genotype).

2. Set up the Punnett square:
\[
\begin{array}{c|cccc}
& Gb & Gb & Gb & Gb \\
\hline
gB & GgBb & GgBb & GgBb & GgBb \\
gB & GgBb & GgBb & GgBb & GgBb \\
gB & GgBb & GgBb & GgBb & GgBb \\
gB & GgBb & GgBb & GgBb & GgBb \\
\end{array}
\]

3. Determine the genotypes and phenotypes of the offspring:
- All offspring have the genotype GgBb.
- Phenotype:
- Hair color: Gg → Gray hair (dominant G is present)
- Eye color: Bb → Black eyes (dominant B is present)
- Phenotype: Gray hair, black eyes

4. Proportions of offspring:
- Since all 16 squares in the Punnett square result in the same genotype and phenotype, all 16 offspring will have gray fur and black eyes.

#### Final Answer for Question 2:
\[
\boxed{
\begin{aligned}
&\text{How many out of 16 have gray fur and black eyes? } 16 \\
&\text{How many out of 16 have gray fur and red eyes? } 0 \\
&\text{How many out of 16 have white fur and black eyes? } 0 \\
&\text{How many out of 16 have white fur and red eyes? } 0
\end{aligned}
}
\]

---

Step 3: Perform Another Dihybrid Cross

#### Question 3:
A male rabbit with genotype GgBb is crossed with a female rabbit with genotype GgBb. We need to fill out the Punnett square and determine the phenotypes and proportions of the offspring.

#### Solution:
1. Identify the gametes produced by each parent:
- Both parents (GgBb) can produce the following gametes:
- GB, Gb, gB, gb

2. Set up the Punnett square:
\[
\begin{array}{c|cccc}
& GB & Gb & gB & gb \\
\hline
GB & GGBB & GGBb & GgBB & GgBb \\
Gb & GGBb & GGBb & GgBb & GgBb \\
gB & GgBB & GgBb & ggBB & ggBb \\
gb & GgBb & GgBb & ggBb & ggbb \\
\end{array}
\]

3. Determine the phenotypes of the offspring:
- Gray hair (G\_): Offspring with at least one dominant G allele.
- White hair (gg): Offspring with the recessive gg genotype.
- Black eyes (B\_): Offspring with at least one dominant B allele.
- Red eyes (bb): Offspring with the recessive bb genotype.

Using the Punnett square:
- Gray hair, black eyes (G\_B\_): 9 squares (GGBB, GGBb, GgBB, GgBb)
- Gray hair, red eyes (G\_bb): 3 squares (Ggbb)
- White hair, black eyes (ggB\_): 3 squares (ggBB, ggBb)
- White hair, red eyes (ggbb): 1 square (ggbb)

4. Proportions of offspring:
- Total squares = 16
- Gray hair, black eyes: \( \frac{9}{16} \times 16 = 9 \)
- Gray hair, red eyes: \( \frac{3}{16} \times 16 = 3 \)
- White hair, black eyes: \( \frac{3}{16} \times 16 = 3 \)
- White hair, red eyes: \( \frac{1}{16} \times 16 = 1 \)

#### Final Answer for Question 3:
\[
\boxed{
\begin{aligned}
&\text{How many out of 16 have gray fur and black eyes? } 9 \\
&\text{How many out of 16 have gray fur and red eyes? } 3 \\
&\text{How many out of 16 have white fur and black eyes? } 3 \\
&\text{How many out of 16 have white fur and red eyes? } 1
\end{aligned}
}
\]

---

Final Summary of Answers:

1. Phenotypes of given genotypes:
\[
\boxed{
\begin{aligned}
&\text{GgbB: Gray hair, black eyes} \\
&\text{ggBB: White hair, black eyes} \\
&\text{ggbB: White hair, black eyes} \\
&\text{GgBB: Gray hair, black eyes}
\end{aligned}
}
\]

2. Proportions for cross GGbb × ggBB:
\[
\boxed{
\begin{aligned}
&\text{How many out of 16 have gray fur and black eyes? } 16 \\
&\text{How many out of 16 have gray fur and red eyes? } 0 \\
&\text{How many out of 16 have white fur and black eyes? } 0 \\
&\text{How many out of 16 have white fur and red eyes? } 0
\end{aligned}
}
\]

3. Proportions for cross GgBb × GgBb:
\[
\boxed{
\begin{aligned}
&\text{How many out of 16 have gray fur and black eyes? } 9 \\
&\text{How many out of 16 have gray fur and red eyes? } 3 \\
&\text{How many out of 16 have white fur and black eyes? } 3 \\
&\text{How many out of 16 have white fur and red eyes? } 1
\end{aligned}
}
\]