An Air Drying Method for the Preparation of Dictyotene Chromosomes from Ovaries of Chinese Hamsters

Abstract

The preparation of meiotic chromosomes from ovarian tissue has been difficult. The dictyotene chromosome stage in particular, which extends from the resting phase to the preovulatory phase of the oocyte, has rarely been observed previously with clear detail. During this stage the bivalents assume an extremely extended form to give an interphase-like appearance of the nucleus when observed in paraffin sections. However, with squash preparations of human embryonic ovary, Ohno et al. (1962) demonstrated dictyotene figures; therefore an interphase-like appearance of the nucleus can be deceptive. Others have used squashing for ovarian meiotic chromosomes in various stages (Borum 1961, Jagiello 1965, Lemon and Morton 1968), and Clendennin (1969) has applied an air drying procedure for meiotic chromosomes in hamster testes. Our procedure applies air drying but differs in several respects from that used by Clendennin and it is especially suited to the preservation and preparation of dictyotene chromosomes.