Formation and biological functions of unusual DNA/RNA structures formed by repeat sequences

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More than 50% of most genomes are tandem repetitive DNA sequences, including telomeres, centromeres, macro-, mini- and microsatellite repeats. Repeats are often genetically unstable, in that they change lengths varying in the number of repeat units in the tracts. Repeat DNAs can exist in unusual structures beyond the canonical right-handed B-form double helix. The specific locations of repeats in genes and chromosomes highlight their biological importance, particularly with respect to the unusual structures they form, which are likely to have functional roles. Evidence indicates that repeat structures play roles in gene regulation, splicing, recombination, epigenetic regulation, repeat length mutation, etc. Functions are likely to be reflected by the biophysical structures formed by the repeats. Importantly, the length of the repeat tracts are hyper-prone to change and these length changes can dramatically affect their biological function. Length changes likely involve unusual structures. Our goal is to understand unusual repeat structures and how they can change lengths.