64 



INBREEDINa AND OUTBREEDING 



^yn 



Gametes of Pj 



QZ^^ 



Individuals of Fj 

 Gray Long 



Gametes of Male 

 All direct segregates 



C-ametes of Feinal( 

 Direct sigre^ates 



S^Z3 r^"^ 



Double recessive 



blacVt vestigial 



used m bacV< crosses 







black 

 Long 

 50. OJ^ 



Gray 

 vestigial 



so.oji 



black 



Lone 



41.5^ 



Gray 



black 



vestigial vestigial 

 41.5^ B,5% 



Gray 



Long 

 8.5% 



FiQ. 21. — Diagram to illustrate linkage breaks or "crossing-over" between the loci 

 containing the factors for the allelomorphic pairs. Gray body, black body and long wing — 

 vestigial wing in Drosophila. (After Morgan.) 



A complete visualization of this series of matings is 

 given in Fig. 21. 



