MENDELIAN SEGREGATION 



25 



chromosomes as readily as one or two. It will not 

 be necessary to give the full analysis, for it will be 

 easily understood from the scheme already given. 

 If a fly with vestigial w r ings is crossed to an ebony, 

 eyeless fly three pairs of factors are involved that lie 

 in different chromosomes. The FI flies are normal, 

 for there is in the hybrid a normal mate for each of 

 the three recessive factors. The possible recombina- 

 tions are shown in the next diagram, Fig. 13. There 



amnnD 



aiiiiiiiD 



OJIIIIIID 



FIG. 13. Diagram to show the segregation of the three pairs of chro- 

 mosomes. Eight combinations are possible, giving 8 kinds of germ cells, 

 with 64 possible re-combinations. 



are four different positions for the chromosome pairs 

 on the spindle, leading to eight kinds of germ cells. 

 By chance meetings of the eight kinds of sperm with 

 the eight kinds of eggs there will result 8 types as 

 follows : 



27 Long, gray, normal eye (wild type). 



9 Vestigial, gray, normal eye. 



9 Long, ebony, normal eye. 



9 Long, gray, eyeless. 



3 Vestigial, ebony, normal eye. 



3 Vestigial, gray, eyeless. 



3 Long, ebony, eyeless. 



1 Vestigial, ebony, eyeless. 



