Variation in the strength of R-reactivity and I-inductivity in inbred lines of Drosophila melanogaster.

Two sets of two sister lines of Drosophila melanogaster, with common genome and cytoplasms of different origin, originally showed intermediate R-effects. All four lines had been kept at constant protocol for about 150 generations. From each of the four lines three sublines were established from single females and the strength of R-reactivity was tested by chromosomal loss technique. In two of the four sets, there was heterogeneity between the sublines. One subline in both cases was similar to the three sublines from the sister lines. The remaining two sets remained unchanged. Specific reactions were found in particular combinations of R- and I-lines. Six sets of independently arising I-lines with K-genome showed different response in the strength of their I-inductivity. The evolutionary relation in the strength of R-reactivity of R-type lines and the implication of the specific reactions are discussed.