A case of an intersex horse with 63,X/64,XX/65,XX,del(Y)(q?) karyotype.

The researchers carried out genetic studies on an intersex horse that had male-like characteristics but incomplete male and female genitalia. They discovered different cell lines in the horse, some of which included parts of a Y chromosome. DNA analysis revealed that some genes and markers usually found on the Y chromosome were missing, suggesting that part of the Y chromosome had been deleted.

Study Background and Horse Description

• The investigated animal in this genetic research study was an intersex horse, with characteristics of both sex types but incomplete development of both male and female external genitals.
• From an overall perspective, the horse had a male body structure, but the genitalia weren’t entirely male or female.

Cytogenetic and Molecular Genetic Studies

• The researchers performed cytogenetic and molecular genetic analyses to understand the genetic composition of this intersex horse.
• Chromosome painting probes were used to detect the cell lines present in the horse. These probes are tools that allow specific chromosomal regions to be highlighted for closer examination.
• Three distinct cell lines were identified in the horse: 63,X, 64,XX and 65,XX with a fragment of a Y chromosome (del Y). This means that some cells had only one X chromosome, some had two X chromosomes, and some had two X chromosomes alongside a part of a Y chromosome.

DNA Analysis

• DNA analysis was carried out using PCR (Polymerase Chain Reaction) and PCR/RFLP (Polymerase Chain Reaction/Restriction Fragment Length Polymorphism) methods, which enable the amplification and specific detection of particular DNA sequences.
• The analysis revealed that there was no presence of specific genes usually found on the Y chromosome, namely SRY, AMELY and ZFY.
• Besides, six Y microsatellite markers, which are repeating sequences of DNA usually found on the Y chromosome, were also absent. These were YM2, YP9, YJ10, YE1, YH12, and YA16.

Final Observations and Conclusion

• The horse’s genetic makeup was found to differ from what would be normally expected either for a male or a female.
• The absence of the genes and markers normally present on the Y chromosome suggested that the fragment of the Y chromosome found might be the result of a deletion of a euchromatic fragment comprising these markers. Euchromatin refers to a segment of the chromosome that’s rich in genes and can manifest in cellular behavior.
• Overall, these findings expand our understanding of chromosomal variations and the genetics behind intersex conditions in animals.