Posted by:
Paul Hollander
at Thu Oct 13 13:59:53 2005 [ Email Message ] [ Show All Posts by Paul Hollander ]
>She's right! Here's a simple formula...
>
>50% bred to another 50% Just multiply .50 x .50 = .25 (25% pos hets)
>
>66% bred to 50% Just multiply .66 x .50 = .33 (33% pos hets)
>
>66% bred to 66% Just multiply .66 x .66 = .44 (44% pos hets)
As I see it, those formulas are too simple. Let's take the first one, 50% x 50%.
0.5 x 0.5 = 0.25 or 25% of the matings are het x het which are identified because they throw a homozygote. The normal babies are 66% probability heterozygous.
0.5 x 0.5 = 0.25 or 25% of the matings are male het x female normal. 0.5 x 0.5 = 0.25 or 25% of the matings are female het x male normal. The probability that a given baby is heterozygous is 0.5 or 50%.
0.5 x 0.5 = 0.25 or 25% of the matings are normal x normal with 0% of having a heterozygous baby.
Add the last three categories because they cannot produce a homozygote; this means that 0.75 = 75% of the matings cannot produce a homozygote. The probability of having one heterozygous animal in the mating is (0.25 0.25)/0.75 = 66%. Statistically, half of the babies from 2/3 of the matings are heterozygous, which means that these babies have a 33% probability of being heterozygous.
On the other hand, for practical purposes, I would sell the babies from all of these matings that do not produce a homozygous baby as normals. 
Paul Hollander
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RE: Correction.... - Paul Hollander, Thu Oct 13 13:59:53 2005