[CHANDA7]

Sir,
In this case the male individuals of the first generation will not be affected, because their x chromosome comes from mother and none of them is affected....

Perfectly right, female non carrier thing is not needed here. Thanks for correcting me. Even if the first mother is a carrier, isn't there always a possibility to have carrier only female progenies? I mean birth of each son/ daughter is an isolated event and there always exists a possibility of unaffected females by being a carrier...

I think the GATE official Answer key is correct.
Let us consider the parent female carrier. The males of 1st generation receives only the affected chromosome from mother while the females receive the unaffected chromosome from their mother.
And the affected males of the 1st generation marry to carrier females. The affected x chromosome from these females pass to the next generation males.
Someone earlier stated that if the female parent is carrier then 50% of the females would be affected.. yes, according to probability, 50% should be affected...but in reality what is the guarantee that the gametes will pass to the next generation strictly according to probability??? And we should keep in mind that pedigree is the pictorial representation of a family.... So in that case, we have to consider all the realistic possibilities.....Not only mathematical calculation.....
If anything wrong, please correct me....
THANKS....

And asn was "115" only.

Sir,
In this case the male individuals of the first generation will not be affected, because their x chromosome comes from mother and none of them is affected....

Perfectly right, female non carrier thing is not needed here. Thanks for correcting me. Even if the first mother is a carrier, isn't there always a possibility to have carrier only female progenies? I mean birth of each son/ daughter is an isolated event and there always exists a possibility of unaffected females by being a carrier...