Question

Your friend Joe has a younger brother Sam and two older sisters. Sam has a strange disorder that has caused his hair to turn green. The doctor says that this is caused by a single gene that is inherited, and that boys are more likely to have green hair then girls. However Joe, his sisters, and both of his parents have normal hair color. Joe does not know much biology and is confused.

Explain to Joe how his brother's condition could have arisen even though Joe has normal hair. Then discuss the likelihood that a) Joe, and b) Sam will have children with green hair. Assume that they both marry women with normal hair color. You will need to include information on meiosis and transmission of genes to assure that Joe understands.
HINT: As part of your answer, indicate the percent of girls vs. boys that you predict would have green hair if fathered by Joe vs. Sam.

Answer 1

It's seems like the green color hair desease is sex sex li recessive trait as only one male is affected while both female are normal

XY father. X. XcX (carrier for green hair mother)

I

XXc XX XcY. XY

Carrier normal affected affected

doughter doughter. Son. Son

So affected son is Sam while normal son is Joe while doughter are elder sister

B) Joe will not have any child affected as he is normal and her wife is also normal

Also Sam all child will be normal

XcY. X. XX   

XcX. XY. Doughter will carrier but phenotypically normal as another X allele is normal while son is normal

Hope it's clear.

Thanks