Mammalian sex chromosomes. VI. Synapsis in the heterochromatin-rich X chromosomes of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica.

This study analyzes the progression of chromosomal synapsis in female meiosis of four rodent species, Mus dunni, Bandicota bengalensis, Mesocricetus auratus, and Nesokia indica. Special attention has been paid to understand the mode of pairing between heterochromatin-rich X chromosomes. The ovaries were obtained from newborn individuals instead of fetuses. In all but M. auratus, day 0 ovaries provided almost all the prophase stages at varying frequencies. In B. bengalensis and M. dunni the entire X chromosomes were paired including the heterochromatin. In M. auratus and N. indica, the heterochromatic arms in a proportion of X bivalents, however, were only partially synapsed. It appears that in these two species heterochromatin association is either delayed or short lived.