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Little Help

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

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Little Help

Postby tironel » Thu May 06, 2010 10:23 pm

A couple who are both carriers of the gene for cystic fibrosis have 2 children who have cystic fibrosis. What is the probability that their next child will have cystic Fibrosis?

*ans-25%*

I need help computing the genotypes of the parents.

I get the genotypes to be XRXr and XRYr????



Also another problem closely related---
An achondroplastic dwarf man with normal vision marries a color-blind woman of normal height. The man's father was of normal height and both of the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant and red-green color blindness is X-linked recessive. How many of their female children might be expected to be color-blind dwarfs?? and how many of their male children would be color blind and normal height??

**ans. 0-female color blind dwarfs && half male color blind normal height**

I have the genotypes as XbXb and XBYa



Any corrections or suggestions would be appreciated!!
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Postby Jillo725 » Fri May 07, 2010 3:00 am

cystic fibrosis is autosomal not sex-linked so the genotypes for the parents would be

Male (Rr) * Female (Rr)

every time they have a child there is a 1/4 chance that they will be homozygous recessive. they're luck just sucks =p

_______

Male (rrXRY) * Female (RrXrXr)

Progeny: RrXRXr rrXrY rrXRXr RrXrY

no female color blind dwarfs, and have of the male progeny are going to be normal height and color blind (not what portion of the total progeny, but the male progeny)
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Re:

Postby JackBean » Fri May 07, 2010 7:02 am

Jillo725 wrote:Male (rrXRY) * Female (RrXrXr)


How can you mark two traits with the same letter? :roll:
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby Jillo725 » Fri May 07, 2010 3:34 pm

my example my rules!

good point though. prolly shouldn't do that.
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Re:

Postby JackBean » Fri May 07, 2010 3:45 pm

Jillo725 wrote:my example my rules!


LOL

Interesting, my rules were not accepted in past... :-/
http://www.biolib.cz/en/main/

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