I need help with the genetic crosses that involves X-linked chromosomes.?

Question

I want to know how to figure out the genotypes of parents and ETC. Any help would be appreciated.

Answer 1

Can you be any more specific.Cus to answer that question with the lack of limitations you currently have specified the best I can do is suggest 4 years of classes in the biology department of an accredited university.

Answer 2

Okay, first off, it's just "X-chromosomes." The phenotypes are "sex-linked" or "x-linked."

Usually a gene is on the X and not the Y. When looking at the crosses, keep in mind that the father will give his sons the Y (and therefore no genes from his X), and his daughters his X.

Mothers give both sons and daughters one of their two Xs.

Answer 3

Let's take an example, a white eyed fruit fly. White eyes are recessive to wild-type (red) eyes. Take a white eyed female fly(ww) and mate it to a wild-type eyed male and all the sons will have white eyed but all the daughters will have red eyes. That's because the gene is on the X-chromosome. The trait was passed from mother to son because the son only has one X chromosome (the other sex chromosome is the Y chromosome.)

To diagram the cross:

ww female x W/Y male
-----> w/Y male (white), Ww females (red)

However, the reverse will not give you white eyes in the progeny:
w/Y male x WW female
--------> W/Y males (red), Ww females (red)

This is a dead giveaway for X-linked traits.

Notice that in each case, Ww females are produced.
Watch what happens now when Ww females are mated to W/Y males.

Ww females x W/Y males
-----> W/Y males + w/Y males (1:1 ratio)
all females will be red eyed (WW and Ww)

If you have further questions, don't hesitate to email me.