[Incorporation of H3-thymidine into the oocytes of a sterlet in the early meiotic prophase]

Abstract

DNA synthesis in meiotic oocytes of the sterlet (A. ruthenus) has been studied during early prophase stages using H3-thymidine. The pattern of H3-thymidine incorporation is similar to that in oocytes of Amphibia and Osteichthyes. In the oogonia as well as in the leptotene and zygotene oocytes, the label is predominantly localized over chromosomes. An intensive incorporation of H3-thymidine into the material of the heterochromatic "cap" has been observed during pachytene. Thus, the main synthesis of extra DNA in the sterlet oocytes occurs during pachytene. No DNA in synthesized by the diplotene oocytes.