Genetics of inbred Drosophila melanogaster. XXV. Simultaneous tests of I-inductivity and M-type.

From a branch of an inbred line of Drosophila melanogaster we introduced the genome into cytoplasms from various sources. Among a pair of sister-lines, which at first showed R-type in the I-R system, one line switched to I-type. From a branch of this I-type line, for several generations kept at 18 degrees C, we established sub-lines derived from four single females. They were propagated at 25 degrees C with 14 or 28-day generation interval, respectively. It was presumed that 14-day generation interval gave strong, and 28 days interval gave weak R-elements. Tests of the strength of the I-inductivity disclosed no relation to the assumed strength of the R-elements. By the same test technique, primary non-disjunction and chromosome loss, the M-type was studied in the eight sub-lines. There appeared diversities in the M-type, assumed to be related to chromosomal mutations. Both primary non-disjunction and chromosome loss were affected by the P-M reaction.