7 children born to an exposed parent or parents have shown, on the basis of incidence of gross anomalies, no evidence of inherited radiationinduced mutations. Theprincipal 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 may take several generationsto affect the phenotype, recognition of their radiation etiology may be extremely difficult. Neel et al. are at present carrving out moresophisticated studies in the Japanese, concerned with the occurrenceof 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 vessels, asymmetry of face. congenital nystagmus, and pigmentation of the cornea. Studies of familial patterns of such defects have not been done; they are not related to exposure. The possible increase in miscarriages andstillbirths among the exposed women duringthefirst 5 vears 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 lymphocytes 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 moresensi- tive tests. However, in view of the relatively small dose of radiation and the smallsize 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. and unexposed). The results, summarized below, included no significant findings indicating radiation-induced mutations. b. The Frequency of “‘Rare'’ Protein Variants. The blood samples mentioned above were sub- jected to electrophoretic analyses for polymorphisms andrare variants of proteins and erythrocyte enzymes.82 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 combined with those of others on Micronesians, and the frequency of rare variants in Micronesians compared withthefrequencies in West European Caucasians, Japanese. and Amerindians. There are many difficultiesin such comparisons, and, although the observedvalues for the four ethnic groups differ by a factor of Table 22 r * - - Gene Frequencie#for Six Genetic Polymorphismsiri the Marshall Islands®? a Phenotype System " i “4 Adenosinedeaminaee =i ts Group specific component Haptoglobin* a Phosphoglucomutase, ** Acid phosphatase , 6-Phosphogluconate dehydrogenase _ . GT 186 56 156 _A 101 164 2-1 18 2 0 50 93 26 2, 32 ft AB B 2 0 73 Total Genefrequency 185 . 168 177 184 b>” 485 185 * ADA! = 0.951 APA = 0.743 Gc} Hp! PGM,! = 0.839 = 0.579 = 0.912 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).