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In the present study, 17 Y-chromosomal STR (Y-STR) loci were typed in 218 unrelated males from Sousse, Central-East Tunisia, to evaluate forensic and population genetic applications of the data. A total of 154 different haplotypes were identified, 127 (82.5%) of which were unique, with the most frequent haplotype occurring in 14 individuals (6.4%). The locus diversity ranged from 0.2050 at DYS392 to 0.8760 at DYS385. The haplotype diversity at the 17-loci resolution was calculated to be 0.9916, while the corresponding values for the extended (11 loci) and minimal (9 loci) haplotypes were estimated at 0.9735 and 0.9710, respectively. Comparison with 29 regional and global populations using correspondence analysis, neighbor joining (NJ) tree, and Rst genetic distance revealed that the Sousse population is highly diverse. This finding is consistent with historical data. Furthermore, the results of this study indicate a distinct genetic substructure among Tunisian populations. In conclusion, the present study demonstrated that the 17 Y-STRs analyzed are highly informative for individual identification, parentage analysis, and population genetic studies.

We describe a female infant with severe abnormal phenotype with a de novo partial duplication of the short arm of the X chromosome. Chromosome painting confirmed the origin of this X duplication. Molecular cytogenetic analysis with fluorescence in situ hybridization (FISH) was performed with YAC probes, further delineating the breakpoints. The karyotype was 46, X dup(X)(p11-p21.2). Cytogenetic replication studies showed that the normal and duplicated X chromosomes were randomly inactivated in lymphocytes. In most females with structurally abnormal X chromosomes, the abnormal chromosome is inactivated and they are phenotypically apparently normal relatives of phenotypically abnormal males having dupX. Therefore, in this case, there is functional disomy of Xp11-p21.2 in the cells with an active dup(X), most likely resulting in abnormal clinical findings in the patient.

Nonspecific X-linked mental retardation (MRX) is a heterogeneous condition in which mental retardation (MR) appears to be the only consistent manifestation. A large genetic interval of assignment obtained on individual families by linkage analysis, genetic, heterogeneity, and phenotypic variability usually are major obstacles to fine-map and identify the related disease genes. Here we report on a large Tunisian family (MRX54) with an MRX condition. X-linked recessive inheritance is strongly suggested by the segregation of MR through seven unaffected carrier females to 14 affected males in two generations. Two-point linkage analysis demonstrated significant linkage between the disorder and several markers in Xp21.3-22.1 (maximum LOD score Zmax = 3.56, recombination fraction 0 = 0 at DXS1202), which was confirmed by multipoint linkage analyses. Recombinant events observed with the flanking markers DXS989 and DXS1218 delineate a refined locus of approximately 2.7 cM in accordance with the physical distance between these two markers. The small interval of assignment observed in this family overlaps not only with nine large MRX loci previously reported in Xp21.3-22.1 but also with two inherited microdeletions in Xp21.3-22.1 involved in nonspecific MR. Although the involvement of several genes located in the Xp21.3-22.1 region cannot be ruled out, data reported in this study could be used as a starting point for the search of such gene(s). Am. J. Med. Genet. 85:276–282, 1999. © 1999 Wiley-Liss, Inc.