Decreased rate of evolution in Y chromosome STR loci of increased size of the repeat unit.
BACKGROUND
Polymorphic Y chromosome short tandem repeats (STRs) have been widely used in population genetic and evolutionary studies. Compared to di-, tri-, and tetranucleotide repeats, STRs with longer repeat units occur more rarely and are far less commonly used.


RESULTS
In order to study the evolutionary dynamics of STRs according to repeat unit size, we analysed variation at 24 Y chromosome repeat loci: 1 tri-, 14 tetra-, 7 penta-, and 2 hexanucleotide loci. According to our results, penta- and hexanucleotide repeats have approximately two times lower repeat variance and diversity than tri- and tetranucleotide repeats, indicating that their mutation rate is about half of that of tri- and tetranucleotide repeats. Thus, STR markers with longer repeat units are more robust in distinguishing Y chromosome haplogroups and, in some cases, phylogenetic splits within established haplogroups.


CONCLUSIONS
Our findings suggest that Y chromosome STRs of increased repeat unit size have a lower rate of evolution, which has significant relevance in population genetic and evolutionary studies.
Department of Evolutionary Biology, University of Tartu and Estonian Biocentre, Tartu, Estonia. mari.jarve@ut.ee
Mari
M
Järve
Lev A
LA
Zhivotovsky
Siiri
S
Rootsi
Hela
H
Help
Evgeny I
EI
Rogaev
Elza K
EK
Khusnutdinova
Toomas
T
Kivisild
Juan J
JJ
Sanchez
D041322:Chromosomes, Human, Y / Q000235:genetics*; D019075:Electrophoresis, Capillary; D005006:Ethnicity; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008957:Models, Genetic; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D013997:Time Factors
D005819:Genetic Markers