MOLECULAR CYTOGENETIC CHARACTERIZATION IN CATTLE USING FISH TECHNIQUE
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Date
2021
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Abstract
A molecular cytogenetic investigation was carried out to screen for chromosomal abnormalities in breeding bulls, to characterize the X-and Y-chromosomes and to determine the sex ratio of X-enriched semen samples. A total of 1072 breeding bulls belonging to 196 Jersey, 10 Holstein Friesian, 626 Jersey crossbreds, 85 Holstein Friesian crossbreds, 81 Kangayam, 33 Red Sindhi, 15 Pulikulam, 12 Vechur, 3 Kasargod Dwarf and 11 non-descript were karyologically screened, before subjecting for the frozen semen production. Analysis of variance revealed a significant difference (P<0.01) in relative lengths of the Y-chromosome between Bos indicus and Bos taurus x Bos indicus crosses. The arm ratio and centromeric index differed significantly (P<0.01) between meta- and sub-metacentric Y chromosomes within the crossbreds.
A Kangayam bull was found to possess a sub-telocentric Y-chromosome, being polymorphic with differences in CBG- and GTG-banding patterns. Karyotyping of a Holstein Friesian crossbred bull revealed an acrocentric Y-chromosome and which was further confirmed with CBG-banding. A case of sex chromosome chimerism (60, XX/XY) was observed in a freemartin calf and male co-twin born to an indigenous cow. The conventional PCR revealed the presence of ZFX and SRY genes in both the animals, while the SYBR green real-time PCR technique quantified high ZFX gene expression levels as 81.66 and 88.35 per cent respectively in freemartin and male co-twin. In addition, a Jersey crossbred female calf with 60, XX complement was diagnosed as a singleton freemartin based on the differential expression of ZFX and SRY genes (97.63 and 2.37 per cent respectively).