28 



GENETIC STOCKS AND BREEDING METHODS 



intercrosses Incrosses 



Backcrosses 



Intercrosses 



(AR/Ar x ARjAr\ 



\ aRjar x aRjar /' 



(AR/Ar x ARjar\ 



\ aRjar x aR/Ar J 



I ARjar x AR/ar\ 



[aR/Ar x «/?/.4r)' 



In the crosses and backcrosses with respect to the r-locus, the inbred strain is on the 

 left, the mutant-bearing animals on the right. 



With respect to the a-locus, the CROSS-incrosses with probability p m each yield 

 BACKCROss-incrosses and these yield iNTERCROSS-incrosses, which thus lead to cross- 



Fig. 7. The cross-backcross-intercross system. 



INBRED 

 STRAIN 



MUTANT 



GENERATION 



CYCLE 

 m 







CROSS 



BACKCROSS 



INTERCROSS 



CROSS 



BACKCROSS 



INTERCROSS 



