Figure Legends Fiaure 1. Isoleucine substitution frequencies versus present ages of the 25 Marshallese. The atomic bomb fallout occurred in March of 1954 so those who are now 21 years old were 1 year old when exposed. ([] QO exposed to 69 R; and #& OR controls. Exposed to 175 R; The computed line for the 5 controls excluding sample 1547 has a slope of 0.0234 X 10° > Xx = 20, y = 2.4038 and x = 50, y = 3.1058. Figure 2. Separation of the a and g chains of sample 24R on carboxymethylcel lulose. Sample dissolved in 5 mM sodium phosphate buffer, pH 6.9; washed into column with 50 mi of the same buffer. Sample eluted with 100 ml of 5 mM sodium phosphate buffer pH 6.9 containing 8 M urea and 50 mM &-mercantoethanol; then a 600 ml linear oradient of this buffer and 40 mM sodium phosphate buffer pH 6.9 containing & M urea and 50 mM 2--ercastoethanol was delivered to the column (1.6 X 40 cm) at a flow rate of 2 mls per minute. Figure 3. Isoleucine substitution frequency versus gamma ray exnosure. The average isoleucine substitution frequency 20 years after exposure is plotted against the exposure these people received in March of 1954. The computed line has a slope of 0.032004 x 10°”; x = 0, y = 3.3125 and n = 100, y = 6.5129,