The evolutionary dynamics of alpha-satellite

alpha-Satellite is a family of tandemly repeated sequences found at all normal human centromeres. In addition to its significance for understanding centromere function, alpha-satellite is also a model for concerted evolution, as alpha-satellite repeats are more similar within a species than between species. There are two types of alpha-satellite in the human genome; while both are made LIP of similar to 171-bp monomers, they call be distinguished by whether monomers are arranged in extremely homogeneous higher-order,multimeric repeat units or exist as more divergent monomeric alpha-satellite that lacks any multimeric periodicity. In this study, as a model to examine the genomic and evolutionary relationships between these two types, we have focused oil the chromosome 17 centromeric region that has reached both higher-order and monomeric alpha-satellite in the human genome assembly. Monomeric and higher-order alpha-satellites oil chromosome 17 are phylogenetically distinct, consistent with a model in which higher-order evolved independently of monomeric alpha-satellite. Comparative analysis between human chromosome 17 and the orthologous chimpanzee chromosome indicates that monomeric alpha-satellite is evolving at approximately the same rate as the adjacent non-alpha-satellite DNA. However, higher-order alpha-satellite is less conserved, suggesting different evolutionary rates for the two types of alpha-satellite.