160 



Linkage and Crossing Over 



Total: 2+p2 

 4 



l-p2 

 4 



l-p2 



AB 



A6 



aB 



ab 



Total : 1+p 



4 

 2-p 



4 

 1-P 

 4 

 P 

 4 



AB 

 A6 

 oB 

 a6 



Fig. 53. General linkage ratios: (a) the F2 ratio from the cross Ab/ 

 AbXaB/aB; (6) the offspring from the cross Ab / aBxAb / ab. In 

 each cross, p is the per cent of crossing over. By substituting the proper 

 value for p, this method can be used for any linked genes. 



