A s*x trait on an X chromosome carreied by the mother: will be carried out but usually not expressed in the?

Question

daughter becausse?

Answer 1

If a mother carries a trait (for example, color blindness) on one of her x chromosomes and has one normal x chromosome, her daughter will have a 50/50 chance of also being a carrier.  This is because the daughter will only get one of the mother's x chromosomes.  The daughter's other x chromosome will come from her father (and, as long as the father's chromosome is normal, the daughter can only be a carrier).  A boy born to this mother has a 50/50 chance of actually inheriting the trait, because he will get a y chromosome from his father.  With only one x chromosome, the boy won't have a normal x from his father to "counteract" the x from his mother.

If the mother actually has the condition (both of her x chromosomes carry the trait), her daughter will automatically become a carrier, and may actually inherit the trait if her father also has the trait.  A boy born to this mother will automatically inherit the trait.  (For example,  all boys born to color blind mothers will automatically be color blind.)

I hope this helps!