TYPES OF FACTOR INTERACTIONS 



169 



The important point involved in this case, however, is the ingenious 

 way in which the investigators made use of the linkage relations and the 

 known fact that crossing-over does not occur in the male in order to study 

 these factors, particularly with reference to their constancy, since they 

 are variable in phenotypic expression. They took a truncate male which 



cf 

 (bT)(pT 3 )X 



(bT)(Pt 3 )X 



(Bt)(pT 3 )X 



(Bt)(Pt 3 )X 



(bT)(pT 3 )Y 



(bT)(Pt 3 )Y 



(Bf)(pT t )Y 



(Bt)(Pt 3 )Y 



(bT)(bT)( P T 3 )XX 

 black pink 9 

 long 



black red 9 

 long 



(Bt)(bT)(Pt 3 )(pT 3 )XX 



Gray pink 9 

 long or truncate 



(Bt)(bT)(Pt 3 )(pT 3 )XX 



Red gray 9 

 long or truncate 



(bT)(bT)( P T 3 )(pT 3 )XY 



Black pink cf 



long 



(bT)(bT)(Pt 3 )(pT 3 )XY 

 Black red d" 

 long 



(BT)(bT)(pT 3 )(pT 3 )XY 



Gray pink cf 

 long or truncate 



(Bt)(bT)(PT 3 )(pT 3 )XY 



Gray red c* 

 long or truncate 



FIQ. 86. Checkerboard analysis of Ft generation obtained by mating an F\ male Droso- 

 phila of the constitution (bT)(Bt)(pT 3 )(Pt 3 )XY with a pink black long female. 



contained the truncate factor and also the truncate intensifier of the 

 third chromosome and mated it to a long-winged black-bodied female with 

 pink eyes. The genetic constitution of the truncate male with respect 

 to the factors involved was (Bt)(B) (Pta) (Pt 3 ) X Y, and the contrasted black 

 female was (bT^^T^pTz^pTs^XX. A male from such a cross is of the 



