Bio queston that i cant answer

[MotivatedToWin]

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

The answer is 2. But I don't know exactly why.

I know that she has to be a carrier so she's heterozygous. The father isnt mentioned but he has to be normal or else he wouldn't exist because it's lethal. So how do I figure the ratio? HELP!

 

[chax1]

If the mother is a carrier then she is heterozygous and the father appears to be normal. So the cross would yield 1 carrier daughter, 1 normal daughter, 1 normal son and 1 aborted son. So the ratio of surviving boys to total surviving children is 1:3. So 1/3 of 6 is 2.

 

[MotivatedToWin]

Wow, I totally didn't see that at all! You pretend like that lethal boy doesnt exist, thank you!