Final answer:
Color blindness is an X-linked recessive trait, meaning it's carried on the X chromosome and can be passed from a carrier mother to her son, who will express the trait if he inherits the affected X chromosome. The concerned woman has a 50% chance of having a colorblind son and a 50% chance of having a daughter who is a carrier.
Step-by-step explanation:
Understanding X-Linked Recessive Inheritance in Color Blindness
A woman who is phenotypically normal but has a maternal grandfather who is colorblind is concerned about the potential inheritance of color blindness in her children. Color blindness is an X-linked recessive trait, which means that it is carried on the X chromosome. Females have two X chromosomes and males have one X and one Y chromosome. This means that males will express color blindness if they inherit an X chromosome with the colorblindness gene, since they do not have another X chromosome to mask the condition.
In the case of the concerned woman, she could potentially be a carrier of the colorblind gene if her mother inherited the gene from her affected father (the woman's grandfather) and passed it to her daughter. Being a carrier, she would not express the trait phenotypically but could pass the gene to her offspring. If she has a son, there is a 50% chance that he will be colorblind, since he would inherit his Y chromosome from his father and has a 50% chance of inheriting the affected X chromosome from his mother.
For daughters, they would inherit a normal X chromosome from their father and either a carrier X chromosome or a normal X chromosome from their mother, making them either carriers or completely unaffected. Therefore, the daughters would not be colorblind but could still pass the trait to their own children. In summary, the concerned woman has a 50% chance of passing the carrier status to her daughters and a 50% chance of having a colorblind son, assuming she is a carrier.