Why Have So Many Tandem Repeats Evolved in Both Coding and Non-coding Regions?
The presence of hundreds of thousands of tandem repeats in the human genome (Buschiazzo and Gemmel, 2010) requires explanation, and understanding their abundance may provide functional insights. It has previously been proposed that tandem repeats can serve as “tuning knobs” in evolution (Kashi et al., 1997; Kashi and King, 2006). Tandem repeat lengths have a digital distribution, as opposed to the usual binary nature of single nucleotide polymorphisms (SNPs), thus providing a wide and continuously variable range of possible genotypes at a given locus (Nithianantharajah and Hannan, 2007). Tandem repeats may enhance the “evolvability” of promoter sequences in yeast (Vinces et al., 2009), although such roles are more difficult to definitively demonstrate in animal species (reviewed in Gemayel et al., 2010). Nevertheless, the genetic diversity provided by tandem repeats may provide a template upon which natural selection can act, via differential fitness associated with development, biolog
