258 ERNST FREESE 



TABLE IV 

 Rates a/;3 of Reversion Induction for Non-Transition Mutants 



Spontaneous 

 backgound of _^ 



Mutant With pH 4. 2 With EES With nitrous acid revertants (10 ) 



r HI 66 70 S3 160 



r 207 57 55 :S2. 5 69 



r 132 55 50 S2 197 



r 157 40 50 S5 175 



r 315 5.0 4. 5 50.2 5.0 



y 102 2.2 3.8 ;:;0. 1 15 



r 105 2.4 3.5 50.1 6. 1 



f 179 2.4 3.4 SO. 05 6.6 



EES 66 4.0 4.5 50.1 5.3 



EES 116 2.9 3.3 50.1 7.8 



P 11 ~1.3 50.8 50.2 ~4.0 



r 114 50.2 50.1 50.1 0.7 



r 131 50.06 <0. 1 <0. 1 0,4 



r 117 <0. 05 <0. 1 <0. 1 0.6 



r 194 50.04 50.1 — 0.5 



r 178 50.01 50.01 50.01 0.02 



r 123 50.01 50.01 — 0.02 



r 289 50.01 50.01 _ 0.1 



EES 122 ;50. 3 <0. 2 _ 1.1 



EES 64 50.1 ;c;0. 2 _ 1.3 



EES 32 50.02 50.2 _ 0.3 



P 12 50.1 _ _ 0.5 



P 5 50.05 50.05 _ 0.9 



P 14 50.04 _ _ 0.1 



P 8 50.03 50.01 _ 0.02 



P 13 50.03 — — 0.3 



P 33 50.03 — — 0.2 



P 3 50.02 50.02 — 0.02 



P 4 50.01 50.02 - 0.08 



P 36 50.01 — — 0.2 



'From E.B. Freese (1!)61) 

 a/P, rate of increase of the frequency of revertants per viable phage and 

 per lethal hit, in units lO"^; r , spontaneous mutants; EES, ethyl ethane sulfonate- 

 induced mutants; P, proflavin-induced mutants;— , not measured; 5 , smaller 

 thEin or about equal to. 



