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Sex linked characteristic

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

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Sex linked characteristic

Postby tironel » Tue May 04, 2010 5:43 pm

Vermilion eyes is a sex-linked recessive characteristic in fruit flies. If a female having vermilion eyes is crossed with a wild-type male, what percentage of the F1 males will have vermilion eyes???

I am given the answer is 75%

How do i determine the parental genotypes?????

How is the answer concluded??
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Postby Jillo725 » Tue May 04, 2010 8:08 pm

the parental genotypes is given in the answer. female with the sex-linked recessive trait is crossed with a wild type male so

female = XrXr * Male = XRY

do a normal punnet square and you get

XrXR XrY

well crap. I'm getting that 100% of the F1 males are the same genotype...XrY so...typo? I don't know.

I asked my bio major roommate and he got the same answer.

It has to be 100%
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Postby tironel » Wed May 05, 2010 12:30 am

that is the answer I was getting, there has to have been a typo---- Thank You
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Postby tironel » Wed May 05, 2010 12:40 am

Also i believe this is a typo as well.......

Barring in chickens is due to a sex-linked dominant gene [B]. The sex of chicks is difficult to determine, but barred chicks can be distiguished from nonbarred at this time. Use this trait so that hatching chicks of one sex are barred, what cross would you make?

-barred male X barred females
-barred males X nonbarred females (correct answer given to me)
-nonbarred males X barred females
-nobarred males X nonbarred females
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Postby jwalin » Wed May 05, 2010 2:17 am

the answer is the third option and not the second
the reasoning being same as above
it isn't what you do that matters but it is how you do it
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Re: Sex linked characteristic

Postby tironel » Wed May 05, 2010 3:13 am

however would a cross with the 3rd option not result with the following genotypes [XBXb, XBY; XBXb, XBy]??
thus all the chicks will posses the trait?
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