Note on the sex chromosomes of the rat during male meiosis

Abstract

[EN] The behaviour of the sex chromosomes has been folowed through meiosis of the male rat. The development of the XY bivalent as a sex vesicle during meiotic prophase was studied. At metaphase I the X and Y are joined at their centromeric ends without any visible chiasma formation. No interstitial chiasmata were ever seen in the sex bivalent, nor the equational mode of separation expected from such chiasmata. The consequence of this behaviour for crossing-over within the sex bivalent was discussed. The heteropycnotic development of the sex chromomes is dependent on the tissue studied: both X and Y were heteropycnotic during meiosis, Y was heteropycnotic in the spermatogonial divisions, neither of them was heteropycnotic in liver tissue.

[ES] Se estudia el comportamiento de los cromosomas sexuales durante la meiosis de la rata macho. También se estudia el desarrollo del bivalente XY, como vesícua sexual durante la profase meiótica. Los cromosomas X e Y, en metafase I, se unen por sus extremos centroméricos, sin formación visible de quiasma. No se vieron quiasmas intersticiales en el bivalente sexual, ni tampoco se observó el modo de separación ecuacional que podría esperarse si existieran tales quiasmas. Se discuten las consecuencias que supone esta conducta para el sobrecruzamiento dentro del bivalente sexual. El desarrollo heteropicnótico de los cromosomas sexuales depende del tejido estudiado. Tanto el X como el Y son heteropicnóticos durante la meiosis; el Y lo es también en las divisiones espermatogónicas y ninguno de ellos lo es en tejido hepático.