A woman with normal color vision has a colorblind daughter. What are the genotypes and phenotypes of BOTH parents?
The mother would have to be a carrier of colorblindness and the father would have to have a colorblind chromosome on the X of his XY make up.. so it would be
mother: 'XX
father: 'XY
The mother is the carrier of colorblindness. The father is colorblind. The genotype is mom:XX, dad:XY
To determine the genotypes and phenotypes of both parents, we need to understand the inheritance pattern of color blindness. Color blindness is typically caused by an X-linked recessive trait, meaning it is carried on the X chromosome. Since females have two X chromosomes, they must inherit two copies of the color blindness allele (one from each parent) to be color blind. In contrast, males only have one X chromosome, so they will be color blind if they inherit the color blindness allele from their mother.
Given that the mother has normal color vision, she must have two normal alleles for color vision (represented as XN). So, her genotype is XNXN. Since she does not have color blindness, her phenotype is normal color vision.
Now let's consider the daughter. If the daughter is color blind, she must inherit the color blindness allele from her father. Since the father is not color blind, he must have at least one normal allele (XN). The other allele he carries on his single X chromosome could be the color blindness allele (Xn) since he is only affected by color blindness if he receives the Xn allele from his mother. Therefore, the father's genotype could be XNXn. However, he could also have two normal alleles (XNXN) and still have a color blind daughter if the mother carries the color blindness allele (Xn). In this case, the daughter's genotype would be XnXn.
To summarize:
Mother:
- Genotype: XNXN
- Phenotype: Normal color vision
Father (possible genotypes):
- XNXn (if he carries one normal allele and one color blindness allele)
- XNXN (if he has two normal alleles)
Daughter:
- Genotype: XnXn (if the father is XNXN and the mother carries the color blindness allele)
- Phenotype: Color blind