Synaptomenal complex analysis of four breeds of Bos taurus taurus x B-taurus indicus hybrids

The synaptonemal complex (SC) was analyzed in four F-1 hybrids of Bos tauru s taurus and B. taurus indicus including Gyr-Simmental(G-S). Nelore Simment al (N-S), Gyr-Holstein-Friesian (G-H) and Nelore-Piemontese (N-P). We analy sed the frequency of various types of SC abnormalities and the frequency of cells with SC abnormalities. The results were compared with similar observ ations made on purebred animals. All the animals studied possessed 29 autos omal and one sex bivalent. The frequency of cells with abnormalities in the hybrids were 28.0 % in the N-P, 29.1 % in the G-S, 33.3 % in the N-S and 4 0.0% in the G-H. The frequency of cells with abnormalities in the four hybr ids was 31.5 %; 57.9 % of these abnormalities occurred in zygotene and 42.0 % occurred in pachytene. The comparisons among the hybrids and among the h ybrids and their parental breeds showed that the only significant differenc e was between Gyr and Gyr-Holstein-Friesian animals, Some aspects of the re lationship between the frequency of cells with anomalies and the fertility of hybrids are discussed.