抄録
Homozygous viability effects of 289 pairs of second and third chromosomes simultaneously extracted from a natural population were measured, separately and jointly. Frequencies of lethal second and third chromosomes were 15.9% and 26.7%, respectively. Random association between chromosome pairs was confirmed. Total homozygous load on two major autosomes was calculated to be 0.791 lethal equivalents per gamete. This total load was partitioned into loads of 0.481, 0.232, and 0.078 due to lethals, mild detrimentals, and severe detrimentals, respectively. The D/L ratio for second and third chromosomes are 0.681 and 0.674. The results indicate that there exists about 7% interchromosomal synergistic interaction between mildly deleterious genes on the two chromosomes, and an interchromosomal epistasis of 10% towards the positive direction was also measured in the artificially combined pairs of two major autosomes. It is remarkable that two cases of “interchromosomal synthetic lethals” were found out of 101, and only in the artificially combined pairs of chromosomes in which variance in the magnitude of interaction was significantly larger than that in natural pairs of chromosomes.
