RESUMEN
The short tandem repeat systems (STRs) HumCD4 (CD4), HumTH01 (TH01) and HumFIBRA (FGA) were amplified by the polymerase chain reaction (PCR) on blood samples from 100 unrelated Yemenians and 100 unrelated Egyptians. PCR products were separated on native horizontal discontinuous gel electrophoresis followed by silver staining. The distribution of observed phenotypes did not deviate from Hardy-Weinberg equilibrium. While significant differences between both Arab populations and an European population from Austria were found at all loci, differences between the Egyptian and the Yemenian samples were found only for CD4. In a number of verified Austrian families (TH01: 426 meioses, CD4: 275 meioses, FGA: 144 meioses) no mutations were found. The observation of a TH01 allele consisting of 4 repeats was confirmed by sequencing. Moreover we report the structure of a TH01 allele 6.3 observed in a Hungarian Caucasian population.