If a recessive genetic disease occurs much more frequently in men than women, which chromosome should be studied as a possible source of the disease?

A recessive disease which is showing sex variation,means it is an #X# linked recessive disease.

Now,#X# linked recessive diseases are expressed more in men than women,as a woman has two #X# chromosomes,one received from father and one from mother,so if she has to suffer from this disease,she needs to have both the #X# chromosomes defective,or else the dominant normal #X# chromosome will take the upperhand and she will become a carrier of that disease.

But,males have one #X# chromosome only,so they are basically hemizygous,that means both the #X# & #Y# characters are expressed in a male.

So,if the male receives an abnormal recessive disease associated gene bearing #X# chromosome,then the disease manifestations will must be seen in him.

So,receving for one defective #X# chromosome, chances of a male getting affected is #100%# but for a female this is #50%# as,the other #X# may be normal or abnormal.

So,disease frequency is high for males.

You can study the following pedigree made,with a normal father and mother as a carrier of colour blindness(#X# linked recessive disease)

In the image #X'# stands for gene responsible for colorblindnes