Cytogenetic evidence of the giant diploid oocytes capable of developing into digynic triploids in the Chinese hamster.

Abstract

The giant eggs twice the normal size in the Chinese hamster 27. Cytogenetic Evidence of the Giant Diploid Oocytes Capable of Developing into Digynic Triploids in the Chinese Hamster were studied cytogenetically with 2 primary and 18 secondary oocytes and 6 one-cell and 5 two-cell zygotes, in order to understand their biological significance as a cause of digynic triploidy. These oocytes exhibited respectively 22 tetrads and 22 dyads with normal morphology, indicating that meiotic chromosomal segregation had taken place normally. The developing giant eggs were all digynic triploids, and the frequency distribution of their two sex variants was 5 cases of XXX and 6 cases of XXY, giving a ratio of nearly 1:1, as expected. Importance of giant diploid oocytes was emphasized as a possible origin of human digynic triploidy.