Probability Of An Allele In Testcross Progeny: Coupling Phase

Repulsion Punnett Square

	p 2 AB	1-p 2 Ab	1-p 2 aB	p 2 ab
p 2 AB	p 2 AB        1 2 B       1 2 B          P 2 b
1-p 2 Ab
1-p 2 aB
p 2 ab

Probability that two allemorphs are contained in the same gamete is (In general):

P(AB) = (1-p)/2 for coupling
P(AB) = p/2 for repulsion
A and B loci are not independent unless p = 1/2

The following is true only when A and B are independent:
If A and B loci are on two non-homologous chromosomes or there is 50% recombination between loci on the same chromosome, then:

P(A) P(B) = P(AB) due to A and B loci segregating independently
P(A) = 1/2, P(B) = 1/2, then P(AB) = 1/4