When a colour blind female offspring is born ?

Options

A. Father is colour blind but mother is carrier
B. Father is colour blind but mother is normal
C. Father and mother both are normal
D. Father is normal but mother is carrier

Answer

To determine when a colorblind female offspring is born, we need to understand the genetics behind color blindness, which is a sex-linked recessive trait. Here’s a step-by-step solution:

### Step 1: Understand the Genetic Basis of Color Blindness
Color blindness is primarily caused by a mutation on the X chromosome. Since females have two X chromosomes (XX), they can be homozygous (normal vision) or heterozygous (carrier) for the trait. Males have one X and one Y chromosome (XY), so they can either be colorblind (XcY) or have normal vision (XY).

### Step 2: Identify the Genotypes of Parents
For a female to be colorblind, she must inherit two copies of the colorblind allele (Xc). This means both of her parents must contribute to her genotype:
- The mother must be either a carrier (XcX) or colorblind (XcXc).
- The father must be colorblind (XcY) since he can only pass on his X chromosome to his daughters.

### Step 3: Determine Possible Combinations
1. If the mother is a carrier (XcX):
- Possible combinations for the daughter:
- Xc (from mother) and X (from father) = Carrier daughter (XcX)
- X (from mother) and Xc (from father) = Colorblind daughter (XcXc)
2. If the mother is colorblind (XcXc):
- The only combination for the daughter:
- Xc (from mother) and Xc (from father) = Colorblind daughter (XcXc)

### Step 4: Conclusion
A colorblind female offspring can be born if:
- The mother is either a carrier or colorblind.
- The father must be colorblind.

### Final Result
Thus, a colorblind female offspring is born when she inherits the colorblind allele from both parents, which can occur if the mother is a carrier or colorblind, and the father is colorblind.

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