Selective staining of Y chromosomal loops in Drosophila hydei, D. neohydei, and D. eohydei.

Modified Giemsa procedures have been developed which elicit differential and highly selective staining of individual Y chromosomal lampbruch loops in spermatocyte nuclei of Drosophila hydei, D. NEOHYDEI, AND D. eohydei. In all three species the Y loop pair known as the "clubs" stains a brilliant dark red with Giemsa at pH 10. With the same treatment other loop pairs either remain unstained, e.g. the "threads", or show a differentiation between light blue and pink staining material, e.g. "pseudonucleolus" and "cones" in D. hydei and D. eohydei. With eosin at pH 2.8 the "threads" in D. hydei can be stained intensely, as well as one matrical component of th "pseudonucleolus". Pretreatment with RNase or TCA removes all stainability from the Y loops with Giemsa at Ph 10. TCA treatment enhances eosin staining at pH 2.8. These and other variations of Giemsa may be utilized to establish homologies between Y loops in different species. The molecular basis of the staining reactions remains to be elucidated.