Simple repetitive sequences and gene expression

Simple repeats are abundant in the eukaryotic genome and can markedly affec t the expression of genes located in their vicinity. The mechanism of this effect involves changes in gene transcription and mRNA sensitivity to cell nucleases, frameshift mutations, etc. The effect depends on the type, lengt h, and location of simple repeats, and is often attributed to their noncano nical conformation (Z form, triplexes, etc.). An ancient origin is assumed for regulation of gene expression with simple repeats.