XIV. 



X RAYS AND X I R R A D I A T I O N 



479 



detecting autosomal sterility factors, gene mutations, lethals, and 

 translocations. Again special Drosophila stocks are necessary for 

 making these tests. The general pattern for the test is schematically 

 drawn in Figure 10. 



Another method for studying irradiation effects is that by which 

 a loss in the chromosome or a specific gene change at a particular 



MATINGS A MATINGS B GENERATION 



MALE PARENT FEMALE PARENT MALE PARENT FEMALE PARENT 



IRRADIATED TESTER STOCK IRRADIATED TESTER STOCK 



_Bx_ £y_ Sb B Cy Sb 



X ^ X I 



Bx Pm H' "^ \Bx Pm H 



TESTER STOCK TESTER STOCK \^ 

 Bx _Pm_ H' Bx Cy Sb Bx Cy Sb B Cy Sb 



~~~X ^ X 2 



/ \Bx Pm H """ Pm 'V \ 



Dominant Y ond \ / Dominant effects 



autosome effects \ / shown here 



shown here \ i/ V 



Bx Pm H Bx Cy Sb Pm H Bx Cy Sb 



y. ~~~ ~ X ^ 



Bx / 



Sex chromosome 

 recessive effects 

 here / 



Bx / Bx \ / 



4 



" Bx 



Recombination of X rayed chromo- Recombination of X rayed autosomes 



somes with themselves shows X roy with themselves shows X rayed 



recessive effects recessive effects 



Fig. 10. Genetic diagram for detection of X-ray effect on autosome. For list 

 of symbols, see Bridges and Brehme (8). 



locus is detected. Such a test may be carried out by irradiating the 

 dominant allele of a gene and mating it to test organisms that carry 

 the recessive allele in homozygous condition. The appearance of the 

 recessive allele indicates either a deficiency, chromosome rearrange- 

 ment, or a mutation to another gene in the allelic series. For tech- 

 nique, see Fryer and Gowen 08). 



3. Cytological Methods 



Cytological methods for the study of X-ray effects depend upon 

 the material exposed to radiation and on the objectives sought. Two 

 general methods are available — one is a paraffin technique, in which 

 tissues for study are imbedded in paraffin, sectioned to a given thick- 



