Bio (genetics) question

[toothhead]

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

The answer is 2. I insist it's zero, but seeing as I'm wrong, can someone please explain it to me?

 

[Donjuan]

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

The answer is 2. I insist it's zero, but seeing as I'm wrong, can someone please explain it to me?

Hey mate, how's the studying going, this problem is a bit tricky. I've struggled with this problem too, and the solution is not something you would notice at first glance. The woman has 6 children, so if we drew one punnet square, we'll only account for four, therefore, we would have to draw two punnet squares to account for the six children.

We're given the woman is a carrier, so let's call her:

XS X - where XS = the gene for spontaneous abortions

XY - the genotype for the normal male. We're assuming she mated with a normal male because either way, a father cannot pass on his X chromosome to his son, only to his grandson, so it doesn't matter whether or not he was affected.

XS X x XY

XS X

X XS X XX

Y XS Y XY

Now draw another punnet square, exactly like this, & cross out the affected males - XsY. The remaining boys, XY, or the normal ones are what the question is asking. The boys aborted, were never born. They're asking how many of her children are boys, so we're assuming the successful ones, and you're left with two normal XY boys. Hope I've helped, & hit me up if you need help with anything else. Good luck studying & with the test

Back to intense bootcamp for me, game day is on Nov 8th, and this is my third time, so pray for me to prevail! Good luck guys!

- Donjuan

 

[sehrmoon]

hey, i had seen this question before but never got the answer...can you please tell me where you found the question n the answer toothhead

 

[Donjuan]

hey, i had seen this question before but never got the answer...can you please tell me where you found the question n the answer toothhead

Hey, its from Topscore

- Donjuan

 

[toothhead]

Hey mate, how's the studying going, this problem is a bit tricky. I've struggled with this problem too, and the solution is not something you would notice at first glance. The woman has 6 children, so if we drew one punnet square, we'll only account for four, therefore, we would have to draw two punnet squares to account for the six children.

We're given the woman is a carrier, so let's call her:

XS X - where XS = the gene for spontaneous abortions

XY - the genotype for the normal male. We're assuming she mated with a normal male because either way, a father cannot pass on his X chromosome to his son, only to his grandson, so it doesn't matter whether or not he was affected.

XS X x XY

XS X

X XS X XX

Y XS Y XY

Now draw another punnet square, exactly like this, & cross out the affected males - XsY. The remaining boyx, XY, or the normal ones are what the question is asking. The boys aborted, were never born. They're asking how many of her children are boys, so we're assuming the successful ones, and you're left with two normal XY boys. Hope I've helped, & hit me up if you need help with anything else. Good luck studying & with the test

Back to intense bootcamp for me, game day is on Nov 8th, and this is my third time, so pray for me to prevail! Good luck guys!

- Donjuan

You're a genius. I didn't even pick up on the word "carries" and assumed both her X genes were faulty. Thanks a bunch for the explanation & good luck on November 8th!! Mine's on November 3rd if it's any consolation.

 

[151AND8TH]

We're given the woman is a carrier, so let's call her:

XS X - where XS = the gene for spontaneous abortions

XY - the genotype for the normal male. We're assuming she mated with a normal male because either way, a father cannot pass on his X chromosome to his son, only to his grandson, so it doesn't matter whether or not he was affected.

A father in this case cannot pass any chromosomes at all -- It cannot exist. Because an XcY would be spontaneously aborted -- so no male could live long enough to be a carrier. correct if I am wrong