478 



JOHN W. G O \V E N 



and gene changes is facilitated by special matings and genetic tech- 

 niques (26,4-1). Special tester stocks are desirable for the test. A 

 genetic diagram of four generations of matings is shown in Figure 9. 



FEMALE 



SC B sm V t 



<c')/ | lethol 1 



P, ! w m Bx X 



' ■ ! I 



I 



* / 



I / 



I t^ 



I SC B sm V t / 



(cl)> | lethol K / 



'' u i /' 



MALE 



J Treated with X rays 



w m Bx 



\ I Stock 



■> 



I SC B sm V t 



f(cl) N lethol I 



w m Bx 



I r 



\< 



\ ^n/ 



T 



/ 

 / \ 



^ 



J/ 



w m Bx 



Bred to w m Bx stock 

 moles to test location 

 of any gene chonges 

 produced 



Dies due to lethal 



Fig. 9. Diagram of matings for detection of X-chromosome muta- 

 tions induced by X rays. 



In the diagram, the following procedure is illustrated: Sperm are ir- 

 radiated within the parent male, which is then mated to tester stock female 

 carrying in one X chi-omosome genes scute(sc), bar(B), small wing(sm), ver- 

 million(v), tan(t), a lethal (not shown) (1), and an inversion to prevent cross- 

 ing over (not shown) (c); in the other X chromosome, the female carries 

 white (w), miniature (m), beadex(Bx). The females in the progeny carrying 

 the bar chromosome and the X-rayed chromosome are chosen and bred to 

 tester males having w m Bx in their X. If the X rays produce a mutant gene 

 or a lethal in the X chromosome this would be observed in all the males of 

 the next generation (Fo) by the mutant change in phenotype, or, if lethal, 

 by the presence of only female progeny. Location of gene change may be 

 made by mating females showing the beadex (Bx) gene. 



A similar method, but applicable to the autosomes, is that for 



