Final answer:
Option B (All daughters have normal color vision, and all sons are color-blind) is correct, as it reflects the inheritance pattern of an X-linked recessive trait like color blindness. Daughters would be carriers with normal vision, while sons would be color-blind.
Step-by-step explanation:
Color blindness is an X-linked recessive trait, which means that the gene causing color blindness is located on the X chromosome and is recessive. Boys have only one X chromosome, so if that chromosome carries the gene for colorblindness, they will be colorblind. Girls have two X chromosomes, so they need two copies of the recessive allele to be colorblind. If a girl has one normal allele and one colorblind allele, she will have normal vision but be a carrier of the trait.
For a color-blind woman (who must have two recessive alleles since she expresses the trait) mating with a man with normal color vision (who has at least one normal allele on his X chromosome), the possible offspring outcomes are as follows:
- All daughters will be carriers, as they inherit one colorblind X chromosome from their mother and one normal X chromosome from their father.
- All sons will be color-blind, as they inherit a Y chromosome from their father (which does not carry the gene for color vision) and the colorblind X chromosome from their mother.
Therefore, the option B. All daughters have normal color vision, and all sons are color-blind would indicate that the color blindness is caused by an X-linked recessive allele.