Is this genetically possible?

Question

This is one of my genetics problems for homework:

Having red eyes in fruit flies is a dominant sex-linked trait carried on the x chromosome.  If a white eyed female is carrying a red eyed gene and mates with a male red eyed fruit fly, what is the probability of the offspring that will have red eyes?

My question is, if the red-eyed trait is dominant, could the white-eyed female have a red-eye gene? Wouldn't she have red eyes if that were the case, or am I just being stupid here?

Anonymous · Accepted Answer

If the red eyed gene is dominant, and the female fruit fly carries it then she has red eyes. She cannot have white eyes if she carries a copy of the red eyed gene.
If she is white eyed and she mates with a red eyed male and the gene is X linked all the female fruit flies will have red eyes and the males will have white eyes 50-50 split
If she carries one red gene and the male has the red gene it will be 75% 25% red to white eyes with all females having red eyes and half of the males having red eyes.
If the female has two red eye genes all of the offspring will have red eyes.

Is this genetically possible?

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