White eye is a sex linked recessive trait in Drosophila. In cross of white eyed female with normal male, what are the phenotype of `F_(1)` generation

Options

A. All normal
B. All males white eyed, all females normal
C. 50% females and all males white eyed
D. 50% males and 50% females white eyed.

Answer

To solve the problem regarding the inheritance of eye color in Drosophila (fruit flies), we need to understand the genetic basis of the traits involved. Here’s a step-by-step solution:

### Step 1: Identify the Genotypes
- The white eye trait in Drosophila is a sex-linked recessive trait. This means that the gene for eye color is located on the X chromosome.
- Let’s denote:
- X^W = X chromosome with the white eye allele (recessive)
- X^N = X chromosome with the normal eye allele (dominant)
- Y = Y chromosome (which does not carry the eye color gene)

### Step 2: Determine the Genotypes of the Parents
- The female Drosophila with white eyes will have the genotype X^W X^W (homozygous recessive).
- The normal male Drosophila will have the genotype X^N Y (hemizygous, as males have one X and one Y chromosome).

### Step 3: Set Up the Cross
- We are crossing a white-eyed female (X^W X^W) with a normal-eyed male (X^N Y).
- The gametes produced by the female will be X^W (only one type, since she is homozygous).
- The gametes produced by the male will be X^N and Y.

### Step 4: Determine the F1 Generation
- The possible combinations of gametes from the parents will lead to the following offspring:
- From X^W (female) and X^N (male): X^W X^N (female, normal eyes)
- From X^W (female) and Y (male): X^W Y (male, white eyes)

### Step 5: Analyze the Phenotypes of the F1 Generation
- The F1 generation will consist of:
- Females: X^W X^N (normal eyes)
- Males: X^W Y (white eyes)

### Conclusion
- Therefore, the phenotypes of the F1 generation will be:
- All females will have normal eyes.
- All males will have white eyes.

The correct answer is: **All males are white-eyed and all females are normal.**

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