37 children born to an exposed parent or parents have shown, on the basis of incidence of gross anomalies, no evidence of inherited radiation- induced mutations. The principal aberrations noted in Marshallese adults and children have been bilateral shortening of the fifth finger, prominent headof ulna,dislocated wrist, enlarged cornea, tortuosity of retinal vessels, asymmetry of face, congenital nystagmus, and pigmentation of the cornea. Studies offamilial patterns of such defects have not been done; they are not related to exposure. The possible increase in miscarriages andstillbirths among the exposed women during thefirst 5 years maylead to speculations that radiation in- duced lethal mutations in germ cells of the ovary or, less likely, in sperm cells.* The presence of chromosomeaberrations in peripheral blood lym- phocytes in the Marshallese 10 years post expo-. sure, and the possible somatic mutation in the hemoglobin, described above, support speculations that mutations in the germ plasm occurred and might be detected in the offspring by moresensitive tests. However, in view of the relatively small dose of radiation and the small size of the population, on a priort grounds a clear-cut demonstration of a genetic effect of radiation in the children born to exposed parents would seem unlikely. Never- theless, given the nature of the circumstances, it has been deemeddesirable to make every effort to collect such data. Since recessive combinations *About one-half the miscarriages occurred in exposed women married to unexposed men. may take several generations to affect the pheno- type, recognition of their radiation etiology may be extremely difficult. Neel et al. are at present carrying out more sophisticated studies in the Japanese, concerned with the occurrence of variant forms of 24 serum proteins and erythrocyte enzymes. He and Dr. R.E. Ferrell kindly consented to examine blood samples collected in 1974 from 187 Marshallese children and parents (exposed and unexposed). Theresults, summarized below, included nosignificant findings indicating radiation-induced mutations. b. The Frequency of “Rare’’ Protein Variants. The blood samples mentioned above were sub- jected to electrophoretic analyses for polymor- phisms andrare variants of proteins and erythrocyte enzymes.8?2 The findings were summarized by Neelet al.8? as follows. ‘Blood specimens from a sample of 187 Marshall Islanders were studied with reference to variants of 24 serum proteins and erythrocyte enzymes. Six of the traits studied exhibited genetic polymorphisms (adenosine deaminase, phosphoglucomutase;, acid phosphatase, 6-phosphogluconate dehydrogenase, haptoglobin, group specific component). There was in addition one ‘rare’ variant (of albumin) in 4047 determinations. These results on rare variants have been combinedwith those of others on Micronesians, and the frequency ofrare variants in Micronesians compared withthe frequencies in West European Caucasians, Japanese. and Amerindians. There are manydifficulties in such comparisons, and, although the observed values for the four ethnic groups differ by a factor of Table 22 o. - - Ne Gene Frequencie#for Six Genetic Polymorphismsint the Marshail Islands®? a Phenotype System Adenosine deaminase Groupspecific component Haptoglobin* 7 . oo "167 ° -. 116 Phosphoglucomutase;** Acid phosphatase “~ 6-Phosphogluconate dehydrogenase : _ 56 156 _A 101 164 2-1 18 50 93 26 AB 73 21 2 Total Gene frequency 0 2, 185 168 ADA! Gel = 0.951 = 0.839 f 184 PGM,! = 0.912 32 B Ul 0 177 485 185 Hp! APA = 0.579 = 0.743 6-PGDA = 0.943 *The Hp® type was observed in 4 individuals. **Two examples of the PGM phenotype 2-7 and a single phenotype 1-7 were observed (PGM,7 =0.008).