Simple sequence repeats as a source of quantitative genetic variation

Trends Genet. 1997 Feb;13(2):74-8. doi: 10.1016/s0168-9525(97)01008-1.


Most traits in biological populations appear to be under stabilizing selection, which acts to eliminate quantitative genetic variation. Yet, virtually all measured traits in biological populations continue to show significant quantitative genetic variation. The paradox can be resolved by postulating the existence of an abundant, though unspecified, source of mutations that has quantitative effects on phenotype, but does not reduce fitness. Does such a source actually exist? We propose that it does, in the form of repeat-number variation in SSRs (simple sequence repeats, of which the triplet repeats of human neurodegenerative diseases are a special case). Viewing SSRs as a major source of quantitative mutation has broad implications for understanding molecular processes of evolutionary adaptation, including the evolutionary control of the mutation process itself.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Animals
  • Gene Dosage
  • Gene Expression
  • Genetic Variation*
  • Genome
  • Humans
  • Phenotype
  • Repetitive Sequences, Nucleic Acid*