BIOLOGY TOP SCORE......Punnit Square Quesiton

[Toothguy80]

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A woman carries a sex-linked lethal gene that causes spontaneous abortions. She has 6 children. How many of her children would you expect to be boys?

So im thinking that
XcX XY
gives
XcX XcY XX XY

only 1 of them is boys, how does she have 6 children..? 😱

 

[KEC029]

A woman carries a sex-linked lethal gene that causes spontaneous abortions. She has 6 children. How many of her children would you expect to be boys?

So im thinking that
XcX XY
gives
XcX XcY XX XY

only 1 of them is boys, how does she have 6 children..? 😱

that's the probability of her having a boy or girl with one fertilization.
so for her to have 6 boys, that whole punnet square needs to happen 6 times and luckly land on XY all 6 times.

 

[Mstoothlady2012]

A woman carries a sex-linked lethal gene that causes spontaneous abortions. She has 6 children. How many of her children would you expect to be boys?

So im thinking that
XcX XY
gives
XcX XcY XX XY

only 1 of them is boys, how does she have 6 children..? 😱

You did that right! which shows that there are 2 boys not 1! yes 1 will die because of the lethal gene. If she gets pregnant 6 times then she can have 6 chidren. The probability of having a boy is 1/2. So then my guess would be that 3 out of 6 children will be boys. May be i dont understand the question.

I hope that helps!

 

[AaBbZz]

Ok so sex linked genes are mostly seen in males because they only need 1 copy of the lethal gene to spontanously abort unlike females which need 2 of the genes.

So we have a heterozygous female (XcX) with a normal male (XY) so for the first cross we have

XcX XcY XX XY four children, 1 dies (the male XcY) leaving 3 children left

But the question says she has six children not 3 so you have to add another one of these crosses which means she has another set of

XcX XcY XX XY four children 1 died leaving 3 children

Now adding the two test crosses together you get 6 children with 2 normal male (XY) 2 normal female (XX) and 2 carrier females (XcX)

So the answer is she has 2 boys and 4 girls of the combined 6 children🙂

When seeing a genetic problem draw all the choices out it makes it much easier to see what the question is looking for.

 

[Toothguy80]

ok, got it
thanks