Visualization of gene transcription in spermatocytes of Drosophila hydei.

X chromosomal and/or autosomal transcriptional activity has been visualized by electron microscopy in primary spermatocyte nuclei of Drosophila hydei lacking a Y chromosome. The spreading technique applied uses a mixture of a hypotonic medium plus a detergent to disperse single germ cells. No effect of the detergent on the quality of the spread was detected using spread rRNA cistrons as a reference. The intervals between the transcripts are highly variable ranging from 0.1 mum to more than 3 mun. The RNP chains exhibit a more or less regular array of particles which reach a diameter of about 550 A. The estimation of transcript lengths leads to molecular weights between 107 daltons and 108 daltons. This is within the range of the huge transcripts of lampbrush loops, so far visualized only in amphibian oocytes.