GBGBGBGB GB GB GB GB: Chapter 10: Dihybrid Cross Worksheet ... - Free Printable

Problem Analysis and Solution

The worksheet involves dihybrid crosses in rabbits, where two traits are being considered:
1. Hair color: Gray hair (dominant, \( G \)) vs. white hair (recessive, \( g \)).
2. Eye color: Black eyes (dominant, \( B \)) vs. red eyes (recessive, \( b \)).

We are tasked with determining the phenotypes and proportions of offspring from given parental genotypes using Punnett squares.

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#### Question 1: Phenotypes of Given Genotypes
We are asked to describe the phenotypes of rabbits with the following genotypes:

1. \( Ggbb \):
- Hair color: \( Gg \) → Gray hair (dominant allele \( G \) is present).
- Eye color: \( bb \) → Red eyes (both alleles are recessive \( b \)).
- Phenotype: Gray-haired rabbit with red eyes.

2. \( ggBB \):
- Hair color: \( gg \) → White hair (both alleles are recessive \( g \)).
- Eye color: \( BB \) → Black eyes (dominant allele \( B \) is present).
- Phenotype: White-haired rabbit with black eyes.

3. \( ggbb \):
- Hair color: \( gg \) → White hair (both alleles are recessive \( g \)).
- Eye color: \( bb \) → Red eyes (both alleles are recessive \( b \)).
- Phenotype: White-haired rabbit with red eyes.

4. \( GgBb \):
- Hair color: \( Gg \) → Gray hair (dominant allele \( G \) is present).
- Eye color: \( Bb \) → Black eyes (dominant allele \( B \) is present).
- Phenotype: Gray-haired rabbit with black eyes.

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#### Question 2: Cross Between \( GGbb \) (Male) and \( ggBb \) (Female)
We need to determine the phenotypes and proportions of the offspring from this cross using a Punnett square.

##### Step 1: Identify Gametes
- Male (\( GGbb \)):
- Only one type of gamete: \( GB \).
- Female (\( ggBb \)):
- Two types of gametes: \( gB \) and \( gb \).

##### Step 2: Set Up the Punnett Square
The Punnett square is set up as follows:

| | \( Gb \) | \( Gb \) | \( Gb \) | \( Gb \) |
|-----|----------|----------|----------|----------|
| \( gB \) | \( GgBb \) | \( GgBb \) | \( GgBb \) | \( GgBb \) |
| \( gb \) | \( Ggbb \) | \( Ggbb \) | \( Ggbb \) | \( Ggbb \) |

##### Step 3: Determine Phenotypes
- Gray fur and black eyes (\( G\_B\_ \)):
- Genotypes: \( GgBb \).
- Count: 8 out of 16.
- Gray fur and red eyes (\( G\_bb \)):
- Genotypes: \( Ggbb \).
- Count: 8 out of 16.
- White fur and black eyes (\( ggB\_ \)):
- No such genotypes exist in the Punnett square.
- Count: 0 out of 16.
- White fur and red eyes (\( ggbb \)):
- No such genotypes exist in the Punnett square.
- Count: 0 out of 16.

##### Final Answer for Question 2:
- Gray fur and black eyes: \( \frac{8}{16} \)
- Gray fur and red eyes: \( \frac{8}{16} \)
- White fur and black eyes: \( \frac{0}{16} \)
- White fur and red eyes: \( \frac{0}{16} \)

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#### Question 3: Cross Between \( GgBb \) (Male) and \( GgBb \) (Female)
We need to determine the phenotypes and proportions of the offspring from this cross using a Punnett square.

##### Step 1: Identify Gametes
- Male (\( GgBb \)):
- Four types of gametes: \( GB \), \( Gb \), \( gB \), \( gb \).
- Female (\( GgBb \)):
- Four types of gametes: \( GB \), \( Gb \), \( gB \), \( gb \).

##### Step 2: Set Up the Punnett Square
The Punnett square is set up as follows:

| | \( Gb \) | \( Gb \) | \( gb \) | \( gb \) |
|-----|----------|----------|----------|----------|
| \( gB \) | \( GgBb \) | \( GgBb \) | \( ggBb \) | \( ggBb \) |
| \( gB \) | \( GgBb \) | \( GgBb \) | \( ggBb \) | \( ggBb \) |
| \( gb \) | \( Ggbb \) | \( Ggbb \) | \( ggbb \) | \( ggbb \) |
| \( gb \) | \( Ggbb \) | \( Ggbb \) | \( ggbb \) | \( ggbb \) |

##### Step 3: Determine Phenotypes
- Gray fur and black eyes (\( G\_B\_ \)):
- Genotypes: \( GgBb \), \( ggBb \).
- Count: 6 out of 16.
- Gray fur and red eyes (\( G\_bb \)):
- Genotypes: \( Ggbb \).
- Count: 4 out of 16.
- White fur and black eyes (\( ggB\_ \)):
- Genotypes: \( ggBb \).
- Count: 4 out of 16.
- White fur and red eyes (\( ggbb \)):
- Genotypes: \( ggbb \).
- Count: 2 out of 16.

##### Final Answer for Question 3:
- Gray fur and black eyes: \( \frac{6}{16} \)
- Gray fur and red eyes: \( \frac{4}{16} \)
- White fur and black eyes: \( \frac{4}{16} \)
- White fur and red eyes: \( \frac{2}{16} \)

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Final Answers

1. Phenotypes:
- \( Ggbb \): Gray-haired rabbit with red eyes.
- \( ggBB \): White-haired rabbit with black eyes.
- \( ggbb \): White-haired rabbit with red eyes.
- \( GgBb \): Gray-haired rabbit with black eyes.

2. Offspring proportions for \( GGbb \times ggBb \):
- Gray fur and black eyes: \( \frac{8}{16} \)
- Gray fur and red eyes: \( \frac{8}{16} \)
- White fur and black eyes: \( \frac{0}{16} \)
- White fur and red eyes: \( \frac{0}{16} \)

3. Offspring proportions for \( GgBb \times GgBb \):
- Gray fur and black eyes: \( \frac{6}{16} \)
- Gray fur and red eyes: \( \frac{4}{16} \)
- White fur and black eyes: \( \frac{4}{16} \)
- White fur and red eyes: \( \frac{2}{16} \)

\boxed{\text{See detailed explanations above.}}