Genetics Problem II

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

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bionewbie
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Genetics Problem II

Post by bionewbie » Wed Jan 25, 2006 5:25 pm

In a cross between a white-eyed female fruit fly and a red-eyed male, what percentage of the femal offspring will have white eyes? (White eyes are X-linked, recessive).

How would the question be different if red eyes are dominant and X-linked? What would the expected phenotypes of the offspring?

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canalon
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Post by canalon » Wed Jan 25, 2006 6:16 pm

Draw you punnet square and results will include both proportion and sex of the offspring.
Patrick

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bionewbie
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Post by bionewbie » Wed Jan 25, 2006 8:21 pm

Yes, my problem is setting up the actual punnet squares ie what are the gametes when the traits are sex linked?

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Jennifer
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Post by Jennifer » Wed Jan 25, 2006 8:35 pm

For sex-lined trait, X and Y are used to represent male and remale gametes. The male is only able to donate one version of the allele, for example:
Since white eyes are recessive, we can use rr to represent them. Since the male can only carry the one allele, we can use R for the dominant red eyes:

XrXr (Female) X XrY (Male)
XR Y
Xr XRXr XrY

Xr XRXr XrY
~*Jennifer*~

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Dr.Stein
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Re: Genetics Problem II

Post by Dr.Stein » Thu Jan 26, 2006 7:22 am

bionewbie wrote:In a cross between a white-eyed female fruit fly and a red-eyed male, what percentage of the femal offspring will have white eyes? (White eyes are X-linked, recessive).

How would the question be different if red eyes are dominant and X-linked? What would the expected phenotypes of the offspring?

I AM sure I already did this somewhere in this forum, but how could and where my post gone away? :? :roll:
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