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A genetic problem .... im not sure if im doing this correct.

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

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A genetic problem .... im not sure if im doing this correct.

Postby xcuteJinax3 » Tue Mar 07, 2006 1:55 am

A black stallion of unknown ancestry was mated to anumber of red mares with purebred pedigrees. These matings produced 20 red offspring and 25 black offspring. Test using the chi-square method indicating whether the hypothesis is acceptable.


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Okay .. I used a punnet square firstly ... I figured that the black stallion would b dominant so that would be BB, and the red mares since they are purebred, they would be bb.

Bb x bb getting a 1:1 ratio (total 2). I saw that the total progeny would be 45, so I got ..... (1/2)*(45) =22.5, then i used the chi square formula ...

(Observed-expected)^2/expected...


[(20-22.5)^2/ 22.5] + [(25-22.5)^2/ 22.5)]



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I'm not sure if my steps are correct at all so can someone please see if I am doing this correctlY? Thanks soo much!
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Postby canalon » Tue Mar 07, 2006 3:06 am

Seems Ok up to the end, but you haven't finish the job. You have to calculate the table coefficient and compare it to your chi sqaure table to tell you if your difference from expeted is significant or not.
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Postby xcuteJinax3 » Tue Mar 07, 2006 4:37 am

Canalon wrote:Seems Ok up to the end, but you haven't finish the job. You have to calculate the table coefficient and compare it to your chi sqaure table to tell you if your difference from expeted is significant or not.



So is the ratio 1:1? That's the part I'm mainly not sure of. :?
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Postby canalon » Tue Mar 07, 2006 4:49 am

That would be your Null hypothesis. A simple gene with a dominant recessive pattern. Your Chi square will tell you if you have to reject or accept it.
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