Non-random position of the A-T rich DNA sequences in early embryos of Drosophila virilis.

Examination of early embryos of Drosophila virilis by light and electron microscopy has shown that the A-T rich satellite DNA sequences have a non-random distribution within the nuclei. As observed by 33258 Hoechst staining and fluorescent microscopy, these sequences are consistently found to be located on the sides of the nuclei nearest to the vitelline membrane. This arrangement of the A-T rich sequences has been observed from the syncytial balstoderm stage into the gastrula stage where, in each nucleus, the satellite DNA sequences remain at a point nearest the topological outside of the organism.