SEX-LINKED INHERITANCE IN DROSOPHILA 91 



L or SRN 9 6 S or LWY & 3 



L or SRB 9 2 S or LWBr d^ 1 



L or SRN d" 3 



L or SRB d" r 



There were seven cases of crossing-over in color, all males, in 

 a total of 872 males, or 1 to 97. Of these seven, three represent 

 one crossing-over (LWN and SWB), and four the counter-cross. 

 In this instance the balance is held despite the lesser viability of 

 the Red-yellows. 



The crossing-over of long, L, (normal) and short, S, (miniature) 

 is shown in the large classes. The linkage is so 'loose,' that these 

 two characters appear almost as though no linkage existed, but 

 an examination shows that where S is combined with RB, and L 

 with Wb the classes of SRB are relatively larger than those of 

 LRB; while conversely the LWY classes are larger than the cor- 

 responding SWY. A comparison of the records with the expecta- 

 tion makes this evident at once. It is most apparent in the males, 

 where no complications exist. Thus LWY cf = 216, while SWY 

 c^ = 85; LWB c^ = 40, while SWB d^ = 30, and on the other 

 hand SRN d^ = 242, while LRN ^ =146; and the SRB cf = 

 82, while LRB cf = 31. The sum of the 'straight' males is 580, 

 while that of the cross-overs is 292. The gametic ratio is there- 

 fore 2:1. 



SHORT, WHITE, BLACK BY LONG, RED, YELLOW 



When the female is SWB and the male LRY the offspring are 

 LRN 9 and SWN &. The results in the next generation are 

 given below: 



SWB 9 by LRY d" 



LRN 9 228 

 ' SWN d" 181 



