508 R. E. COMSTOCK AND H. F. ROBINSON 



tative character to be studied is affected by seven pairs of genes that are dis- 

 tributed as follows in the parent lines: 



Line A —BiBi bo bo b^ bz b^ biB-^B^B^B^ b-, b^ 

 Line B—b^b^BoBoB^BiBiBib-^b-.b^bJi^B-, 



with w's and a's having the following values: 



Locus 



Note that less than complete dominance has been assumed for every locus. 

 Gene frequencies should be one-half in an F2, so ^^2^(1 — q)n" becomes 

 |Sm"^ and 2^(1 — q)ahi- becomes \l^aht^. Substituting numerical values of u 

 and a listed above, we obtain 



and 



2^(1 -(/) a%2 = 2.57 



Now assume the following recombination values for })airs of loci: 



Thus the seven loci fall in three groups that are either on three separate 

 chromosomes or, if on the same chromosome, far enough apart to allow free 

 recombination. In an F2 the values of p, r, s, and / will depend on v, the re- 

 combination value, and the original linkage phase as follows: 



p r s t 



Coupling (l-t')/2 v/2 v/2 {l-v)/2 



Repulsion.... v/2 (l-i')/2 (l-i')/2 v/2 



Hence {pi — rs) takes the following values: 



Coupling. . 

 Repulsion . 



