One form of hemophilia is caused by a sex-linked recessive gene. assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. what is the probability that their first son will have hemophilia?

When a haemophilic carrier female marries a haemiphilic man then due to ther genotypes 
 
Xc=carrier of haemophilia
Xn=normal 
Y=dont carry haemophilic genes
so here we go!
        XcY         cross with      XcXn
 
 genotypes of ther offsprings
    1=XcXc      
    2=XcXn   
    3=XcY
    4=XnY     
so from whole 4 there is 50% parobability 

           

The mother inherited her father's X chromosome so her genotype is XHXh and she produces XH and Xh gametes. 

The father's genotype is XhY and he produces Xh and Y gametes. 

The possible outcomes are XHXh normal female (carrier), XhXh (affected female), XHY (normal son) XhY (affected son) 

So the probability of an affected daugher is 1.4

Orbit is represented by the blank space