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Topic:Chromosomes
Chromosomes in horses are structures composed of DNA and proteins that carry genetic information crucial for the development, functioning, and reproduction of equine species. Horses typically have 64 chromosomes, organized into 32 pairs, which include one pair of sex chromosomes that determine the genetic sex of the individual. Chromosomal analysis in horses is used to study genetic disorders, inheritance patterns, and species evolution. Variations or abnormalities in chromosome number or structure can lead to developmental issues and impact fertility. This page compiles peer-reviewed research studies and scholarly articles that explore the structure, function, and implications of chromosomal variations in equine genetics and breeding.
Cytogenetic studies of three equine hybrids. A detailed investigation of testicular meiosis in a mule, a hinny and a Przewalski horse/domestic horse hybrid were made. Abnormalities of pairing were observed in the mule and hinny in most germ cells at the pachytene stage of meiotic prophase, and spermatogenesis was alsmot totally arrested. A few mature spermatozoa were recovered from the ejaculate and epididymal flushings of the hinny. The Przewalski horse/domestic horse hybrid was fertile and showed normal spermatogenesis. Chromosome banding studies showed a close homology between the karyotypes of the Prezwalski horse (Equus przewalskii,...
An intersex (male pseudohermaphrodite) horse with 64XX/XXY mosaicism. The clinical, pathological and chromosomal findings in a male pseudohermaphrodite horse are reported. This animal appeared to be a female but showed strong male sexual behaviour. A small penis emerged from a rudimentary vagina. Two small testes were present in the abdomen and undifferentiated seminiferous tubules contained only supporting cells. No uterus was found. Culture of peripheral blood leucocytes revealed a 64XX/65XXY mosaicism.
XO-gonadal dysgenesis in the mare (report of two cases). TWo cases of XO-gonadal dysgenesis in the mare are presented. Case No 1 was a pure 63, XO, while Case No 2 was a mosaic with a preponderance of XX cells. The clinical picture was one of phenotypically normal female mares with small uteri and infantile ovaries. The ovaries lacked germ cells, and consisted of stroma only. This study emphasizes the importance of chromosome analysis in providing information concerning the mechanisms involved is some cases of equine infertility.
Further studies on the cell populations of an intersex horse. An intersex horse exhibiting cell types of different sex chromosome constitution was subjected to further studies in order to determine whether the house was a mosaic or a chimera. Cultures of gonadal tissue and peripheral blood revealed mainly 64/XX and 64/XY cells, the former predominating in both tissues. The frequency of drumstick-bearing poly-morphonuclear neutrophils in the intersex horse was similar to that noted in normal mares. Blood type analysis using 17 naturally occurring agglutinins and hemolysins revealed partial agglutinations with three antibodies for the factors of the A syst...
An equine intersex with unilateral gonadal agenesis. Cytogenetic and histological studies have been carried out on an intersex horse which was clinically diagnosed as a cryptorchid. The horse had the general conformation of a stallion but the external genitalia included a well developed vulva and a penis. The right testis which was descended was devoid of germ cells and the left "gonad" located in the cavum vaginale contained neither testicular nor ovarian tissue. The male duct system on both sides were relatively well developed despite the absence of a testis on the left side. Chromosome analysis on cultured cells from the descended testis reve...
CHROMOSOME COMPLEMENT: DIFFERENCES BETWEEN EQUUS CABALLUS AND EQUUS PRZEWALSKII, POLIAKOFF. The chromosome number of the domestic horse is 2n = 64; different races have the same complement. The chromosomes of two Przewalski's horses (at Catskill Game Farm, New York), presumably ancestral wild horses from Mongolia, are identical: 2n = 66, with more acrocentric and fewer metacentric elements than the chromosomes of the domestic horse. This apparent difference in karyotype may help resolve the questions of "purity" in the relatively few remaining Przewalski's horses. Moreover, these findings are of interest in relation to the apparent fertility of hybrids between these species.
Chromosome Study Of An Alleged Fertile Mare Mule. This study is oriented towards explaining the usual infertility observed in mule and hinny species through a detailed investigation of their chromosomal structures, with a special emphasis on the instances [...]
Changes of somatic chromosomes of the horse in serial in vitro transfers. In two tissue culture lines, HS and HF, which originated from foetal horse tissues, the changes of chromosomes were studied in the course of serial in vitro transfers. It was found that the two cell lines under consideration were characterized by specific changes in chromosome pattern different from each other. HS underwent transformation from diploidy to hyperdiploidy. HF may have been in a process of transformation from diploidy to tetraploidy. Evidence derived from this study indicates that several courses for chromosome transformation exist, and that generalizations predicting a single pat...
Population Genetic Analysis of the Estonian Native Horse Suggests Diverse and Distinct Genetics, Ancient Origin and Contribution from Unique Patrilines. The Estonian Native Horse (ENH) is a medium-size pony found mainly in the western islands of Estonia and is well-adapted to the harsh northern climate and poor pastures. The ancestry of the ENH is debated, including alleged claims about direct descendance from the extinct Tarpan. Here we conducted a detailed analysis of the genetic makeup and relationships of the ENH based on the genotypes of 15 autosomal short tandem repeats (STRs), 18 Y chromosomal single nucleotide polymorphisms (SNPs), mitochondrial D-loop sequence and lateral gait allele in DMRT3. The study encompassed 2890 horses of 61 b...
