Question

If a father passes on a certain disease to all his daughters, he would have a defective allele on the chromosome(s).

• A. X
• B. Y
• C. X and Y
• D. either X or Y

Answer 1

The correct option is A X

X-linked dominant disorders are caused by mutations in genes on the X chromosome, one of the two sex chromosomes in each cell. In females (who have two X chromosomes), a mutation in one of the two copies of the gene is sufficient to cause the disorder. In males (who have only one X chromosome), a mutation in the only copy of the gene causes the disorder. The daughters by default inherit one X-chromosome from the mother and one X-chromosome from the father. If the father is affected, it means he has the defective allele on the X-chromosome which he has passed on to his daughters.