Turner syndrome is one of the most common chromosomal abnormality syndromes [1], affecting 1 in 2,500 live born females. It is characterized by short stature, gonadal dysgenesis, a variety of somatic features (neck webbing, cubitus valgus, high arched palate, short neck and widely spaced nipples) and major organ malformations (e.g., congenital heart disease, structural renal abnormalities) [2,3]. Nearly half of the patients have a classical 45,X karyotype, while the remainder have structurally abnormal sex chromosomes or are mosaics with cell lines including mos 45,X/46XY [4-6]. The percentage of mosaicism with a cell line that contains a normal or abnormal Y chromosome is about 5.5% using cytogenetic analysis [6]. Approximately half of the unidentifiable marker chromosomes that have an estimated frequency of 3% are Y-derived [6,7]. It has been speculated that most Turner syndrome patients with putative non mosaic 45,X karyotype have an undetected mosaicism, based on an analysis which revealed that less than 1% of 45,X conceptions survive pregnancy [8]. Several investigators have postulated that in 45,X patients, fetal survival needs mosaicism in at least some organ or tissue [8,9]. Patients with the SRY gene require special attention since the presence of a Y chromosome correlates with a 10-20% risk of developing gonadoblastoma or dys­germinoma later in life [10,11]. Gonadoblastoma is an in situ malignancy of the dysgenetic gonad with variable age of appearance and considerable malignancy potential, and dysgerminomas and other malignant germ cell tumors can arise within the gonadoblastoma [10,11]. The critical region for development of gonadoblastoma has been tentatively localized to a 1-2 Mb region near the centromere of the Y chromosome [12].

      Sex determination and differentiation are sequential processes regulated by an unknown number of gene loci located on sex and autosomal chromosomes that occur in the testis-determining pathway. The SRY gene on Yp, a single exon gene that codes for a protein of the HMG-box-domain family of DNA-binding proteins has been shown to play a major role in sexual differentiation, being the primary testicular determinant [13-20].          

      Kocova et al. [21], reported that the SRY gene is present in about 33.3% of Turner syndrome patients, using the Southern blot technique after polymerase chain reaction (PCR). Others have shown a variable percentage of SRY gene-positive Turner syndrome patients [5,7]. Detection of this gene in patients with or without cytologically-detected sex-chromosome mosaicism has important clinical and therapeutic implications [21,22]. Using a combination of conventional cytogenetic methods and molecular DNA analysis for the SRY gene, we have studied 40 Turner syndrome patients from the Republic of Macedonia to estimate the frequency of Y mosaicism and compare our results with those in the literature.