A human female will definitely be a colour blind it

Options

A. both of her parents are also colour blind.
B. her mother is a carrier and her father is a colour blind.
C. her mother carries the allele for colour blindness on both X chromosomes.
D. her father is a colour blind and her mother is normal.

Answer

To determine whether a human female will definitely be color blind if both of her parents are color blind, we need to understand the genetics behind color blindness.

### Step-by-Step Solution:

1. **Understanding Color Blindness**:
- Color blindness is often caused by a mutation in the genes responsible for color vision, located on the X chromosome. It is typically inherited in an X-linked recessive manner.

2. **Genetic Makeup of Parents**:
- Since both parents are color blind, we can denote their genotypes. The mother (female) has two X chromosomes, and if she is color blind, her genotype is XcXc (where Xc represents the X chromosome with the color blindness allele).
- The father (male) has one X and one Y chromosome. Since he is color blind, his genotype is XcY.

3. **Determining the Offspring's Genotype**:
- When these parents have a daughter, she will inherit one X chromosome from each parent. The mother can only pass on an Xc chromosome (since she is XcXc), and the father can pass on either an Xc or a Y chromosome. However, since the daughter will inherit an X chromosome from the father, she will inherit Xc from the mother and Xc from the father.

4. **Conclusion**:
- Therefore, the daughter’s genotype will be XcXc. Since she has two copies of the color blindness allele, she will definitely be color blind.

### Final Answer:
A human female will definitely be color blind if both of her parents are color blind.

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