Goal Identification of latent mosaicism and determination of a parental origin of an X chromosome in TS patients in Uzbekistan.

Methods Molecular genetic studies are carried out in 35 patients with TS (26 with monosomy, 9 with mosaicism) at the age of 7 to 16 and their parents.

Results Three X-linked markers (DMD 49, AR and DX1283E) were studied on the basis of their high level of heterozygosis, a number of alleles (11 to 19) and localization both on a short and long X chromosome arm. The results obtained confirm that the use of a set of these primers (DMD 49, AR and DX1283E) will allow enhancing a probability of obtaining an informative marker and detection of latent X-mosaicism. Monozygosity on all 3 markers indicates the presence of only one X chromosome that in female patients will correspond to true monosomy. Heterozygosis of one marker suggests on the presence of an additional second X chromosome or a part of an X chromosome which is observed both in 46XX karyotype (healthy) and in mosaic variants of chromosomal anomalies (45X0–46XX, 45X0–46?Y).

Conclusions A comparative analysis of polymorphic markers in TS patients and their parents enable us to establish the origin of an X chromosome and determine in gametogenesis of which parents meiotic impairment occurred. Identification of mosaicism in Turner syndrome is very important from the viewpoint of setting correlations between a phenotype and karyotype.