wae wo. > * 1 . : -* =e at eh Daehe DON ey ae ae Ld ieeLS ee es Da ee ae UNCLASSIFIED ‘BIOLOGYAND MEDICINE an effort to determinethe extent to which strontium 90 is likely to be ingested by the human ~ population. Samples have been obtained thus.far from the Philippines and ‘Turkey, and a team ' in Libya will collect samples from that country. Plans were under way to expand the program into a number of Latin American countries, and initial contacts were made with officials con- cerned with nutrition. An AEC representative will visit these Latin American countries during the summer of 1957 to discuss the program and enlist needed participation.. MOUSE GENETICS A conference on mouse genetics. sponsored by the British Medical Research Council was held at Harwell on April 26to ensure that similar studies of radiation-induced mutations at: specific loci in mice being carried out by the United Kingdom and the United States do not overlap but complement one another. The conference was attended by the principal geneticists of the Harwell project and three”geneticists prominent in the AEC prograni. ; The results of studies made at the Oak Ridge National Laboratory by Russell and at Harwell by Carter were compared, and the following significant statistics reported: \ woe Number of Exposure. Investigator (roentgens) Carter (U.K.) Oo, Ruasell (U.S.) Combined Carter (U.K.)_ Russell (U.S.} Russell (U.S.} Russell (U.S.) 0 o| 37.5 300 600 ‘ 1,000 — ‘Mice. oO _ rate per locus 63,116 - 40° 7 Mutations 164,687 297,803 - 34,998 | 37,189 72,472 31,816 Mutation. 9° «7 if 4 23 75. 2i . Induced mutations © per locus .. per-roentgen «(xk 10") (x 1078) 4 oe 6.0 6.9 16.3 88.3 147.9 94.3 ‘ - 25.17 27.1 23.5 8.7 NOTE: The apparent drop in the induced mutation rate when the exposure is increased from 600 to 1,000 roentgens is‘ caused by a substantial increase in the death rate at the higher exposure. The technique used in both the Carter and Russell studies is based on (1) the fact that most mutations are recessive, that is, they must be inherited from both parents to produce a visible effect on the individual, and (2) a “specific locus”test, which was devised to detect such recessive mutations in offepring. A stock of mice was built up to be pure recessive for seven different mutant genes, each one producing a visible characteristic such as short ears, dilute hair color, or white spotting. Females of this stock were mated to males with all normal genes but which had been irradiated (or not irradiated in the control series). In the résulting offspring a recessive trait of the | mother appeared only if there had been a mutation of exactly the same kind in the father’s i germ cells (i.e., at the same locus in the chromosome) as that responsible for the trait in the mother. ’ UNCLASSIFIBD =