Sex Ratio among the Children of Atomic-bomb Survivors (1948-1962)
In the past, lethal recessive mutations of the X chromosome were thought to alter the birth sex ratio in favor of females if mothers were exposed to radiation, since the single X chromosome in males is derived from mothers, and in favor of males if fathers were exposed, since the male X chromosome is transmitted only to daughters. Early observations concerning births to A-bomb survivors (1948-1953) favored this hypothesis but were not statistically significant. Further data collected through 1962 (140,542 births, 73,994 with one or both parents exposed) did not support any radiation effect on sex ratios.
Subsequent considerations regarding errors in sex chromosome number and patterns of X chromosome inactivation in embryonic and extraembryonic tissues have made it difficult to determine how X chromosome mutations may affect sex ratios. Under these circumstances, it seems doubtful that sex ratio measurements can be useful as indicators of genetic radiation damage.