PRINCIPLES OF GENETICS 



19 



duced. The grandparental types constitute 60 per cent 

 and the crossovers 40 per cent of this second generation. 

 A study of crossing-over has shown that all possible 

 percentages of crossing-over occur, up to nearly 50 per 

 cent. If exactly 50 per cent of crossing-over took place, 



-A. 



"604 



40 0-/, 



Fig. 14. 



The inheritance of two sex-linked characters, white eyes and forked 

 bristles, and red eyes and normal bristles. 



