Transcription from the X chromosome dose sensitive promoter of <i>Sxl</i>, <i>Sxl_Pe</i>, is reduced in embryos homozygous for the <i>msls</i>.

In situs on embryos with an early transcript specific probe reveals two dots/nucleus at the sites of transcription on the X chromosomes during cycles 13 and 14 in development. The roX double mutants had a reduction in expression in most embryos as all the females are mutant, the msls showed reduced expression in about 50% of the embryos (crosses described in text). The ‘sibs’ panels show the signal from normal looking cycle 14 embryos in the same collection, presumably the heterozygous siblings. NA – not applicable. All embryos photographed at 40× mag.