抄録
The frequency of deleterious second chromosomes carrying recessive lethal or semilethal genes has been surveyed for the past 15 years in the Anyang, Korea, population of Drosophila melanogaster. It remarkably increased from about 32% (1973) to 45% (1978) and then decreased to about 30% (1983). The rise and fall of the deleterious chromosomes consisted of two similar but phase-shifting changes in lethal and semilethal frequencies. The latter occurred two or three years after the former change. The allelism rate among lethal chromosomes increased during the period, especially from 1971(0.55%) to 1980 (3.68%). Comparison with other data from the same population suggested that some mutator factors, such as the P element, may have invaded the Anyang population in the sixties.
