Genetics 43 



Fig. 3.1 I Different results in double crossing-over. A, two-strand 

 exchange; B, four-strand exchange; C, D, three-strand exchange. 

 (Adapted from De Robertis, Nowiruski, and Saez, 1954, General 

 Cytology, 2d ed., W. B. Saunders Company; ami White, 1954, Animal 

 Cytology and Evolution, 2d cd., Cambridge University Press.) 



(a) 



ib) 



(c) 



id) 



