Characterization of a novel dimorphism in the 5' flanking region of the short tandem repeat (STR) locus,c-fes/fps (FES)

The FES short tandem repeat (STR) locus contains seven to 14 repeats of the tetranucleotide sequence ATTT. A novel 10 base pair dimorphism in the 5' flanking region of the FES locus was characterized in four broad populations: African-American, Hispanic, Caucasian, and Asian. The absence of the 10 base pair sequence, or (-) allele, was closely linked to FES STR alleles with 10 or fewer repeats. The presence of the 10 base pair sequence, or (+) allele, was closely linked to FES STR alleles with 12 or more repeats. The (-) and (+) alleles occurred equally often in FES STR allele 11. The nucleotide sequence (5'-GGCTGTTTTG-3') of the (+) allele, located 179 base pairs upstream of the FES STR, was determined to be consistent within and among the four populations. Statistical and sequence analysis confirmed the linkage between the two polymorphic sites. The results indicate that the exclusion rate of the FES locus is increased, above that for the STR alone, when both polymorphic characteristics are considered.     

Sequence variation at three X chromosomal short tandem repeats in Caucasian and African populations

Sequence variation for the X chromosome short tandem repeats (X-STRs) DXS9898, DXS6789 and GATA172D05 was studied in two major population groups, namely Caucasians and Africans. DXS6789 revealed two different subtype sequence polymorphisms: for shorter alleles, with less than 17 repeats, results showed a simple composition with the following structure: (TATG)_m-(TATC)_n. For longer alleles, a constant TATC insertion was observed at the beginning of the variable repeat unit. Additionally, alleles identical in size revealed structural variations regarding the TATG/TATC proportion. Africans showed a higher intra-allelic variation at this locus than the Caucasian population group. For all three loci, DXS9898, DXS6789 and GATA172D05, no unique structure was found among Africans and Caucasians.