Question

Evolution: population genetics

The following are all equivalent definitions of the coecient of linkage disequilibrium given in class:
D = g_AB - ps
= pt - g_Ab
= qs - g_aB
= g_ab - qt
where p is the frequency of the A allele, q is the frequency of the a allele, s is the frequency of
the B allele, and t is the frequency of the b allele.

For a given set of allele frequencies (p; q; s; t), what is the maximum attainable value of D (hint: it is not 1/4).

If p = 0:7 and s = 0:3, what are the expected chromosome frequencies under linkage equilibrium?

What are the chromosome frequencies when D is at half of its maximum attainable value?

Answer 1

Maximum attainable value of D Dmax+ In whichever is smaller is the maximum attainable value of D P-0.7 P+q1 so, qF0.3 S(x)-0.3 s+t-1 so, t(y) 0.7 Dmax qs-0.3*0.3-0.09 Or Dmax-pt-0.7*0.7-0.49 Maximum attainable value of D 0.09 Expected chromosome frequencies under linkage equilibrium: fAs-ps-0.7*0.3-0.21 fab qt-0.3*0.7-0.21 fAb pt-0.7*0.7-0.49 fas qs-0.3*0.3-0.09