In rabbit black skin (B) is dominant over brown skin (b) and short hair (S) is dominant over long hair (s). If homozygous black-short haired male is ceossed with a homozygous brown-long haired female. All `F_(1)-`offspring are heterozygous black-short haired. `F_(1)` male crossed with `F_(1)` female. In `F_(2)` generation what is the percentage of homozyhous black-short haired offspring :-

Options

A. `50%`
B. `12.5%`
C. `6.25%`
D. `18.75%`

Answer

To solve the problem step by step, we will analyze the genetics of the rabbit skin color and hair length traits.

### Step 1: Identify the Genotypes of the Parents
- The male rabbit is homozygous for black skin and short hair, so his genotype is **BBSS**.
- The female rabbit is homozygous for brown skin and long hair, so her genotype is **bbss**.

### Step 2: Determine the Genotype of the F1 Generation
- When these two rabbits are crossed, all offspring (F1 generation) will inherit one allele from each parent.
- The F1 genotype will be **BbSs** (heterozygous for both traits), meaning all F1 offspring will have black skin and short hair.

### Step 3: Cross the F1 Generation
- Now, we need to cross an F1 male (BbSs) with an F1 female (BbSs).
- This is a dihybrid cross, and we can set up a Punnett square to determine the genotypes of the F2 generation.

### Step 4: Set Up a Punnett Square
- The gametes from each F1 parent can be: **BS, Bs, bS, bs**.
- The Punnett square will be a 4x4 grid, resulting in 16 possible combinations for the F2 generation.

### Step 5: Determine the Genotype Ratios
- From the Punnett square, we can count the genotypes:
- **BBSS** (homozygous black-short) = 1
- **BBSs** (heterozygous black-short) = 2
- **BbSS** (heterozygous black-short) = 2
- **BbSs** (heterozygous black-short) = 4
- **bbSS** (homozygous brown-short) = 1
- **bbSs** (heterozygous brown-short) = 2
- **Bbs** (heterozygous black-long) = 2
- **bbss** (homozygous brown-long) = 1

### Step 6: Calculate the Percentage of Homozygous Black-Short Offspring
- The only homozygous black-short haired offspring is **BBSS**.
- Out of 16 total offspring, there is 1 BBSS.
- To find the percentage:
\[ \text{Percentage of BBSS} = \left(\frac{1}{16}\right) \times 100 = 6.25\% \]

### Final Answer
The percentage of homozygous black-short haired offspring in the F2 generation is **6.25%**.

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