Autosomal vs sex-linked trait

[mcdull1016]

By looking at a pedigee of three generations, how can we determine if the condition is autosomal or sex-linked?

I am very confuse about this. Sometimes, the situation can be both sex-linked and autosomal. My TA didn’t explain this well.

What does it mean by autosomal trait? What does it mean by sex-linked trait?

From my TA’s explanation, sex-linked trait is mean by if the female got it … all her sons will have it. is that the case? i dun really get this.

Thanks in Advance!! XD

[Poison]

Sex-linked traits are carried with the chromosomes X or Y. Autosomals are carried like other genes.

quote :

From my TA’s explanation, sex-linked trait is mean by if the female got it … all her sons will have it. is that the case? i dun really get this.

Read the following carefully and think about it, the answers are here:
Lets have a look at a hypothetic condition to understand this better. Lets say a trait (maybe a disease) called ‘a’ is carried by X ( a recessive one) . And lets show it like: X^a. Have a look at the conditions for a female: XX (normal), X^aX (carrier), X^aX^a (ill).
Take carrier female into consideration with a normal male like: XY
Their children can be: XX (normal female), X^aX (carrier female), XY (normal male), X^aY (ill male).
So you can say that if the mother is a carrier there is a possibility of her son to be ill or normal. If we are talking about a X-linked trait, there is no possibility for the father to transfer it to his son. And his daughter will be a carrier, but not ill. (if the mother is normal)
Another point: If the mother is ill -means: X^aX^a, it is %100 percent sure that her son will be ill (the son—-> X^aY) Her daughter can be ill (if the father has that trait too) or carrier (means she can tranfer it to her children).
Hope it is clear now. Don’t hessitate to ask if something is confusing for you. 🙂

PS: wow I can’t believe myself, did I type this??? 😯

[mcdull1016]

that helps me clear up my confusion on sex-linked trait … how about autosomal? does that mean it is other chromosomes that contribute to that trait?

[Poison]

Autosomals are carried like every other gene. Let’s have an exmaple:

A is a dominant trait and a is a recessive trait (means maybe a disease). The possibilities for the people (no matter female or male) are: AA, Aa, aa.
AA: normal
Aa: carrier
aa: ill

To determine if a trait is autosomal or sex-liked take care of the sex of the children. If we are talking about, lets say, a disease, there will be something like: A male child, whose mother is ill, is normal. You can understand that, that trait can not be a X-liked one.
Hope it is clear now.

[leanbeans]

are u still unclear bout this after poison’s explanantion?
If u are.. u can PM me cuz I’ve got a whole sheet on how to tell if a trait is autosomal (recessive or dominant) or X-linked.

cheers. 😀

[ncortiz]

hi, im interested in that sheet about determining sex-linked or autosomal… i would really appreciate it.. you could send it to me as an attachment.. at ncortiz@stthomas.edu

-thank you!

[vermaankit]

In the answer given above you are saying that female has ressasive X^a trait and the male children with genotypr X^aY will be ill but it may be possible that Y is dominat in that case how male children will be ill.??please clear my doubt..

[Author]

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