INDEPENDENT MEN DELI AN INHERITANCE 



89 



The F 2 population produced by mating two FI individuals will be 

 made up of F\ gametes as shown in the checkerboard analysis in Fig. 

 43. When like phenotypes are collected the ratio in each sex is 3 long 

 red: 3 long white:! vestigial red:l vestigial white. This is very 

 different from the typical 9:3:3:1 ratio of a dihybrid, but it is strictly 

 in agreement with experimental observations and chromosome behavior. 



The reciprocal cross gives different results and for that reason we 



V(wX) 



v(wX) 



VY 



vY 



V(WX) 



V(wX) 



v(WX) 



FIG. 43. Checkerboard analysis of the F* obtained by crossing vestigial white 9 with 



long red cf in Drosophila. 



V(WX) 



v(WX) 



VY 



vY 



FIG. 44. Checkerboard analysis of the Ft obtained by crossing long red 9 with vestigial 

 white cf Reciprocal of cross analyzed in Fig. 43. 



shall go through it briefly to show that this difference is a necessary con- 

 sequence of the chromosome behavior. When a long red female, genetic 

 formula VV(WX)(WX), is mated to a vestigial white male, vv(wX)Y, the 

 FI individuals are long red females, Vv(WX}(wX], and long red males, 

 Vv(WX)Y. The FI females then give the same four types of eggs as 

 those of the reciprocal cross, viz., 



V(WX) V(wX) v(WX] v(wX). 



