Final answer:
The colorblind daughter's genotype is XXc. The parents' genotypes are XcX (mother and carrier) and XY (father with normal color vision). The father of the colorblind daughter does not have to be colorblind. Colorblindness inheritance patterns explain this situation.
Step-by-step explanation:
Explanation of Colorblindness Inheritance
If a man whose parents have normal color vision marries a woman who also has normal color vision, and they have a daughter who is colorblind, her genotype must be XXc (where Xc represents the colorblind allele). Since colorblindness is an X-linked recessive trait, the daughter must have inherited one recessive colorblind allele from each parent. Therefore, the mother must be a carrier of the colorblind allele (heterozygote with genotype XcX), and the father must have a normal color vision allele on his X chromosome (XY) and contribute the Xc allele to his daughter. As for the paternal grandparents, since the father has normal color vision, his mother can have a genotype of either XX or XcX, and his father must be XY since he is male and does not carry a second X chromosome.
Answers to the additional questions are as follows:
- It is not necessary for the father to be colorblind since he has only one X chromosome which can carry either the normal vision allele or the colorblind allele.
- A woman can have colorblindness if she inherits two recessive alleles (one from each parent), even if her father does not exhibit colorblindness.
- If a woman is colorblind but her sister has normal color vision, their parents are likely to be a carrier mother (XcX) and a father with normal vision (XY).
The sex chromosomes of a male are XY, while those of a female are XX. The father determines the sex of the child because he contributes either an X or Y chromosome, while the mother always contributes an X chromosome.
Sex-linked inheritance is when a gene causing a trait or disorder is located on a sex chromosome, often the X-chromosome, which makes the trait more common in males since they have only one X chromosome. A son cannot inherit colorblindness from his father as the son inherits his father's Y chromosome and the X chromosome comes from the mother.
Red-green colorblindness is a common inherited trait because it is X-linked and males have only one X chromosome, making it more probable for them to express the trait if they inherit the recessive allele.