Colorblindness Inheritance: Probability of Affected Daughters

To determine the probability of their daughter being colorblind, we need to consider the inheritance pattern of red-green colorblindness. Since it is a sex-linked recessive trait, the genes responsible for color vision are located on the X chromosome.

The father is mentioned as having normal color vision, which means he must have two normal copies of the gene responsible for color vision (one on each X chromosome). We can represent his genotype as XN Y, where XN represents the normal allele and Y represents the Y chromosome that does not carry the genes for color vision.

The mother is not specified to be colorblind or have normal vision. However, since red-green colorblindness is a recessive trait, she must carry at least one copy of the colorblind gene (Xc) on one of her X chromosomes to be a carrier. Her genotype can be either XcXc (if she is colorblind) or XN Xc (if she is a carrier).

If the mother is XN Xc (carrier) and the father is XN Y, there are four possible outcomes for the genotype of their daughter:

1. XN XN: This genotype results in normal color vision. The daughter receives one normal allele (XN) from each parent.

2. XN Xc: This genotype also results in normal color vision. The daughter receives the normal allele (XN) from her father and the carrier allele (Xc) from her mother. She becomes a carrier like her mother.

3. Xc XN: This genotype results in red-green colorblindness. The daughter receives the colorblind allele (Xc) from her mother and the normal allele (XN) from her father. However, since females have two X chromosomes, the normal allele compensates for the colorblind allele, and she will have normal color vision. She will be a carrier like her mother.

4. Xc Xc: This genotype also results in red-green colorblindness. The daughter receives the colorblind allele (Xc) from both her mother and her father. Since both X chromosomes carry the colorblind allele, she will express the trait and be colorblind.

Therefore, if the mother is a carrier (XN Xc) and the father has normal color vision (XN Y), there is a 25% chance that their daughter will be colorblind (Xc Xc) and a 75% chance that she will have normal color vision (XN XN, XN Xc, or Xc XN).