[Study, on isolated nuclei, of the dynamics of chromosome changes in female germ cells in early human embryos]

Sixteen human female embryos at the age of 33-35 days and 7, 9, 10, 11 weeks of development have been studied. Isolated nuclei of the sex and somatic cells have been obtained from embryonic gonads. Total air-dried preparations have been stained with fluorochrome "Hoechst 33258" and studied under the luminescent microscope. In the nuclei of gonocytes, at the moment when incorporation into the gonad takes place, sex chromatin, as well as structural heterochromatin, is absent. Beginning from the oogonia stage up to the preleptotene, a progressive condensation of chromatin is observed; heterocyclic X chromosome appears. When the preleptotene is completed, heterochromatized x chromosome disappears.