Abstract
Evidences for paternal transmission of delta in D. melanogaster were presented. The Cy/S-5 daughters derived from the mating, Cy/S-5_??_×Cy/Pm_??_, did not show any symptoms for retention of delta (Minamori 1969). However, females of later generations of the Cy/S-5 line derived from the above mating produced a characteristic segregation distortion which indicates the presence of delta. The distortion became larger with later generations and reached a definite level which was expressed by females of the original Cy/S-5 strain. These findings indicate that delta may be transmitted through male flies, although the amount transmitted may be minute, and it may be gradually accumulated in the above line extending over many generations. The accumulation of delta appeared to be delayed in the lines derived from Cy/S-5 males of later generations after repeated backcrossing of the male to Cy/Pm females.
It was recognized that a total of 224 males sampled from the original Cy/S-5 strain and of 208 Cy/S-5 males sampled from the thirty-first generation of backcrossing had transmitted delta to their offspring, and no delta-free lines were obtained. Based on these facts, the nature of delta was discussed.
