F Repulsion Progeny Part I

AaBb x AaBb F progeny

One should expect 9:3:3:1 ratio w/o linkage

With repulsion linkage we expect:

We can derive the expected proportions of each of the classes of zygotes using a Punnett square. We use the concept of independence for the probability of male and female gametes uniting. We are not assuming independence between the A and B loci.

	P/2 AB	(1-p)/2 Ab	(1-p)/2 aB	p/2 ab
p/2AB	AABB p2/4	p(1-p)/4	p(1-p)/4	p/4
(1-p)/2Ab	p(1-p)/4	(1-p)/4	(1-p)/4	p(1-p)/4
(1-p)/2aB	p(1-p)/4	(1-p)/4	(1-p)/4	p(1-p)/4
p/2 ab	p/4	p(1-p)/4	p(1-p)/4	p/4 aabb

Let us collect like terms.

class	Proportion	A_B_ Phenotype
AABB	p/4
AABb	p(1-p)/4
AaBB	p(1-p)/4
AaBb	p/4
AABb	p(1-p)/4
AaBb	(1-p)/4
AaBB	p(1-p)/4
AaBb	p(1-p)/4
AaBb	p/4

 p + p + p + p(1-p) + p(1-p) + p(1-p) + p(1-p)
 4     4     4       4           4          4            4
+ (1-p) + (1-p)
     4           4

= 3p + 4p(1-p) + 2(1-p)
    4         4           4

= 3p + 4p - 4p + 2(1 - 2p + p)
                    4

= 3p + 4p - 4p + 2 - 4p + 2p
                    4

= p + 2
      4

= P(A_B_)