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Updated: Jun 16, 2026

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes
Published on: May 11, 2017
Numerical sex chromosome aberrations and abnormal sex development in horse and sheep
G P Di Meo1, G Neglia, A Perucatti
1National Research Council, ISPAAM, Laboratory of Animal Cytogenetics and Gene Mapping, Naples, Italy.
Abstract:
Gonadal dysgenesis and heterosexual conditions are often associated with sex chromosome abnormalities. In this study we report on 2 cases of abnormal sex development involving numerical sex chromosome aberrations in both horse and sheep. A 17-month-old Standardbred filly was sent to an equine fertility centre as an embryo donor due to its reduced size, being much smaller than a racehorse filly of the same age, which excluded it from an athletic career. External genitalia were clinically normal but manual palpation of the reproductive tract showed the presence of a small underdeveloped uterus and ovaries, as confirmed by ultrasonographic examination. Cytogenetic investigation by CBA-banding revealed an abnormal karyotype with X chromosome monosomy (2n = 63,X). A 18-month-old ewe showed distinct heterosexual traits with presence of a vulva (with enlarged clitoris), well-developed abdominal testes and mammary glands. Internal sex adducts were atrophic as seen after mating. Cytogenetic analysis revealed the presence of XX/XY mosaicism.
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