MOLECULAR CHARACTERIZATION OF RIBOSOMAL GENES ON THE Y^bb- CHROMOSOME OF DROSOPHILA MELANOGASTER

Sharyn A. Endow ¹

¹ Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710

The question of whether the Y^bb- chromosome contains ribosomal genes has been examined by using Southern blot analysis and comparing rDNA hybridization patterns for X/X and X/Y^bb- DNA. The results demonstrate that the Y^bb- chromosome contains sequences that hybridize to an rDNA probe under stringent conditions. Differential hybridization of some of these sequences with DNAs corresponding to different regions of a complete ribosomal gene repeat provides evidence that some of the genes on the Y^bb- chromosome are type 2 repeats. Because data obtained by other workers suggest that type 2 repeats are transcribed only to low levels, these repeats may be classed as "nonfunctional". A further finding is that the ribosomal genes on the Y^bb- chromosome do not undergo multiple rounds of DNA replication during polytenization of X/Y^bb- cells.