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so confused and need help with some questions

Genetics as it applies to evolution, molecular biology, and medical aspects.

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so confused and need help with some questions

Postby I suck @ biology » Wed Feb 15, 2006 11:51 pm

well this is my first time on here but i just really need help understanding somethings about genetics and if you can help it would be Great! :) sooo...

"you have found a new mutant phenotype in fruit flies that you suspect is recessive and sex linked. what is the single, best cross you could make to confirm your predictions?" - so would a cross be like mating that fly with a homozygous fly with dominant traits? but would that show that its sex linked? :?
secondly...
"a woman is a carrier for a sex-linked lethal gene that causes spontaneous abortions. she has nine children. how many of these children do you expect to be boys?"- now i believe that since its the mother passing it on, that it is more likely to effect a son..? and if that is true then she would have less boys since they would be aborted..? or does it stay at a 50% chance?

So as you see i'm pretty confused when it comes to sex-linked genes and all and i'm hoping that someone can help me understand it better. Thanks! :D
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Postby army » Thu Feb 16, 2006 6:47 am

It's a kind o' challenging question! :lol: I'd be really like to answer 'em if I were you. :D though it's a bit confused :?

let me guide you... (But actually I ain't sure you'd understand.. :( )

"you have found a new mutant phenotype in fruit flies that you suspect is recessive and sex linked. what is the single, best cross you could make to confirm your predictions?" - so would a cross be like mating that fly with a homozygous fly with dominant traits? but would that show that its sex linked?


I think the answer is 'yes'. Recessif phenotype will not appear when you mate recessive homozygous fly with one which dominant homozygous. But, you have to notice that --in this case-- you expect that it is sex linked. If it is sex linked, the trait would be inherited by one gender only, not both male and female filial inherit them. :wink:

"a woman is a carrier for a sex-linked lethal gene that causes spontaneous abortions. she has nine children. how many of these children do you expect to be boys?"- now i believe that since its the mother passing it on, that it is more likely to effect a son..? and if that is true then she would have less boys since they would be aborted..? or does it stay at a 50% chance?


Mmmm...
Heterozygous girls (or carrier) may live also. See that the mother stays alive eventhough she is a carrier?
That's true that she may have less boy. In above case, it could be 3 boys ar3 given birth.
Yeah, the precentage of the probability that she will give birth for a boy will be 33.33% :D
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Postby I suck @ biology » Thu Feb 16, 2006 8:59 pm

Thanks so much for the help! i really appreciaite it! plus i understand it a bit more :D
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Postby Dr.Stein » Mon Feb 20, 2006 6:45 am

Yes, and I hope you would change your name by then ;) :D
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