Why is it that-- although there are very few genes located on the Y chromosome --?

Question

human males may suffer from having just one copy of the X chromosome, while females have two?

This part is really confusing to me so please answer and explain... Thank you!

Answer 1

I'll start with an eg. Haemophilia A is an X linked disorder. So this disorder is found on X chromosome we'll call it X^ .
A Normal X is called X*.
A normal male has X*Y
and a
normal female has X*X*....

So if a male inherited the abnormal X^ they would have X^Y.
So they will be affected 100%. Because they only have 1 X chr.

On the other hand chicks, have 2 X Chromosome's.... So if she had X^X*. The normal X* will overide the abnormal X^. She will only Express the X*.
So she wont be affected. But will be a carrier, and possibly pass it on to 50% of either of her children.(males will be affected, females carriers, if she marrys a normal male)

Hope i made sense.

Answer 2

Since females have two X chromosomes, females have a "second chance" when it comes to any recessive disorders. A common example is color-blindness. If females get the allele for color-blindness (which is on the X-chromosome), they still have a second X chromosome that probably has the dominant allele for normal color vision. Very, very few females are colorblind because of this second chance. If males get the allele for color-blindness on the X from Mom, then they have no "second chance" or "second opinion" because they have no second X-chromosome. The Y-chromosome does not have any of the genes that the X has. So males are more likely to be color-blind, to have hemophilia, and so on.

Answer 3

because females only use one of their copies of X. the other is deactivated in what is called a "bar body"