A homozygous red eyed female was mated with white eyed male, a daughter from `F_(1)` generation was also mated with white-eyed male. Red eye is dominant over white eye and is a sex linked trait. In the progeny from this second mating.

Options

A. all males and females have red eyes
B. all males and females have white eyes
C. all males have red eyes, all females have white eyes
D. males and females have red eyes and white eyes in the ratio of 1:1

Answer

To solve the problem step by step, we will analyze the genetic crosses involving Drosophila, focusing on the inheritance of eye color, which is a sex-linked trait.

### Step 1: Identify the Genotypes of the Parent Generation
- The homozygous red-eyed female has the genotype **X^R X^R** (where X^R represents the red eye allele).
- The white-eyed male has the genotype **X^r Y** (where X^r represents the white eye allele).

### Step 2: Determine the Genotype of the F1 Generation
- When the red-eyed female (X^R X^R) is crossed with the white-eyed male (X^r Y), the offspring (F1 generation) will all inherit one X chromosome from each parent.
- All daughters will have the genotype **X^R X^r**, which means they will have red eyes because red is dominant over white.

### Step 3: Cross the F1 Female with a White-Eyed Male
- The F1 female (X^R X^r) is then mated with another white-eyed male (X^r Y).
- The gametes produced by the F1 female will be **X^R** and **X^r**.
- The gametes produced by the white-eyed male will be **X^r** and **Y**.

### Step 4: Set Up a Punnett Square
- Create a Punnett square to visualize the possible offspring from this cross:

| | X^r (white-eyed male) | Y (white-eyed male) |
|---------|------------------------|----------------------|
| **X^R** | X^R X^r (red-eyed female) | X^R Y (red-eyed male) |
| **X^r** | X^r X^r (white-eyed female) | X^r Y (white-eyed male) |

### Step 5: Analyze the Offspring Genotypes
- From the Punnett square, we can see the possible genotypes of the offspring:
- **X^R X^r**: Red-eyed female (50%)
- **X^R Y**: Red-eyed male (50%)
- **X^r X^r**: White-eyed female (25%)
- **X^r Y**: White-eyed male (25%)

### Step 6: Determine the Phenotypic Ratio
- The phenotypic ratio of the offspring from this second mating will be:
- 50% red-eyed females
- 50% red-eyed males
- 25% white-eyed females
- 25% white-eyed males

### Step 7: Final Ratio
- Therefore, in the progeny from the second mating, the ratio of red-eyed to white-eyed individuals is 1:1 for males and females.

### Conclusion
The correct answer is that the progeny from the second mating will have red eyes and white eyes in the ratio of 1:1.

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