Factors influencing disproportionate replication of the ribosomal RNA cistrons in Drosophila melanogaster.

This report describes studies of the compensatory response employing D. melanogaster stocks that bear cloned-X chromosomes derived from laboratory populations of strains Oregon R and Canton S. We find that modification of the autosomal background in either the female or the XY male parent influences the expression of the compensatory response by X chromosomes derived from the Canton S population, whereas Oregon R isolates are unresponsive to these effects. We have also studied compensatory replication in X/O larvae produced from cloned-X derivatives of both Canton S and Oregon R. Canton S larval compensation exceeds that of the adult, whereas in Oregon R the converse is true. We have concluded that both X chromosomal and autosomal factors affect the expression and magnitude of the compensatory response.