Sexing of mouse eggs at the first cleavage division by the use of C-staining method.

Abstract

One-celled eggs were recovered from mated, colchicine-primed dd female mice, and chromosome preparations were made by the air-drying and C-staining methods. Their mitotic stages were mostly at late prometaphase with two haploid groups of chromosomes and at early metaphase, a stage of syngamy, and partly at the chromatid stage of metaphase. The Y, a small chromosome with no C-band, was distinguished not only at the chromatid stage of metaphase but also at the other stages above-mentioned. Out of 2, 053 eggs examined 767 eggs could be sexed, sexing rate being 37.4%. Of these, 334 eggs were identified as males and 433 females, with a sex ratio of 43.5% males. The sex ratio was further classified according to the stages above-mentioned. Sex ratio before syngamy was significantly higher than that at syngamy and the chromatid stage of metaphase.