A Mammalian X-O Sex-Chromosome System in the Monotreme Tachyglossus aculeatus Determined from Leucocyte Cultures and Testicular Preparations

Abstract

The chromosomal complement of the monocreme Echidna has been found to be 64 in the female and 63 in the male which is the heterogametic sex. This indicates an XX female, XO male sex-chromosome mechanism. Metaphase chromosome spreads were obtained from the testis and from leucocyte cultures. Details of conditions of culturing Echidna leucocytes from peripheral blood are given