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MUTATION AND PLANT BREEDING 



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LU 



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34 68 



35 270 540 1080 2160 4320 



r-UNITS 



Figure 11. — Reverse mutations induced in met-2 auxotrophs by vari- 

 ous doses of X-rays. After Demerec and Sams (34). 



that a selective mechanism was responsible for the nonlinearity. A 

 recent case of nonlinearity has been found in mice in which mutation 

 rate is dose-rate dependent (133). It was also reported in this paper, 



