Dinucleotide (CA)n tandem repeats on the human X-chromosome and the history of the Mediterranean populations

Abstract

Background: Tandem repeats (STRs) are genomic markers of particular interest in forensic and population genetics. Most of the population data currently available correspond to the variation of STRs of forensic panels, which barely include dinucleotide tandem repeats.

Aims: The aim of the study is to test the usefulness of a battery of dinucleotide STRs on the X chromosome for population and forensic studies.

Subjects and methods: A total of 672 individuals from 12 Mediterranean populations and two external references were analysed for 15 X-STR following the instructions of the commercial company and using control DNA from the CEPH centre whose sequences are published in GenBank. Genotypic results were analysed using standard population genetics methods including estimates of linkage disequilibrium, population structure and gene flow. Common forensic efficiency parameters were calculated.

Results: The analysed X-STRs show high values of genetic diversity, comparable to other STRs of more common use. No significant associations between markers were found. A slight population structure was detected between the two shores of the Mediterranean. The X-STRs studied here present a similar degree of variability to that of other X-STRs used in forensics.

Conclusion: Tandem-repeated dinucleotides are a good tool for evidencing population differences here. Forensic parameters indicate that the dinucleotide X-STRs are suitable for forensic use.

Keywords:

• CA dinucleotide STRs
• X-chromosome
• human populations
• Mediterranean region

Conclusions

In summary, the 15 dinucleotide X-STR set offers an interesting tool for human population genetics. The analysed markers present very high values of genetic diversity, equivalent to those shown by other STRs included in the most used panels. In addition, the population information they produce is very comparable to that detected with massive genomic data. Further analyses in new populations and with larger population sizes would be desirable to confirm the value of this type of genetic marker for population studies.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by the Spanish Ministry of Science and Technology under the BMC2001–01224 project to PM and the Secretaria de Estado de Educación y Universidades under the FPU predoctoral grant AP2002–1030 to JS.