information:extraction
Effects on proteins

Mutations in these repeating segments can affect the physical and chemical properties of proteins, with the potential for producing gradual and predictable changes in protein action. For example, length changes in tandemly repeating regions in the Runx2 gene lead to differences in facial length in domesticated dogs (Canis familiaris), with an association between longer sequence lengths and longer faces. This association also applies to a wider range of Carnivora species. Length changes in polyalanine tracts within the HOXA13 gene are linked to hand-foot-genital syndrome, a developmental disorder in humans. Length changes in other triplet repeats are linked to more than 40 neurological diseases in humans, notably trinucleotide repeat disorders such as fragile X syndrome and Huntington's disease. Evolutionary changes from replication slippage also occur in simpler organisms. For example, microsatellite length changes are common within surface membrane proteins in yeast, providing rapid evolution in cell properties. Specifically, length changes in the FLO1 gene control the level of adhesion to substrates. Short sequence repeats also provide rapid evolutionary change to surface proteins in pathenogenic bacteria; this may allow them to keep up with immunological changes in their hosts. Length changes in short sequence repeats in a fungus (Neurospora crassa) control the duration of its circadian clock cycles.