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Human accelerated regions (HARs), first described in August 2006,[1][2] are a set of 49 segments of the human genome which are conserved throughout vertebrate evolution but are strikingly different in humans. They are named HAR1 through HAR49 according to their degree of difference between humans and chimpanzees (HAR1 showing the largest degree of human-chimpanzee differences of the 49). Found by scanning through genomic databases of multiple species, some of these highly mutated areas are thought to have contributed to the development of human neuroanatomy, language, and complex thought.

Characterisation of HAR1-HAR5 regions, from Pollard et al., 2006.[2]

Several of the HARs encompass genes known to produce proteins important in neurodevelopment. HAR1 is an 118 base pair stretch found on the long arm of chromosome 20 overlapping with part of the RNA genes HAR1F and HAR1R. HAR1F is active in the developing human brain. The HAR1 sequence is found (and conserved) in chickens and chimpanzees but is not present in fish or frogs that have been studied. There are 18 base pair mutations different between humans and chimpanzees, far more than expected by its history of conservation.[1]

HAR2 includes HACNS1 a gene enhancer "that may have contributed to the evolution of the uniquely opposable human thumb, and possibly also modifications in the ankle or foot that allow humans to walk on two legs". Evidence to date shows that of the 110,000 gene enhancer sequences identified in the human genome, HACNS1 has undergone the most change during the evolution of humans following the split with the ancestors of chimpanzees.[3]

HAR-associated genes[edit | edit source]

See also[edit | edit source]

Ultra-conserved element

References[edit | edit source]

  1. 1.0 1.1 Pollard KS, Salama SR, Lambert N, Lambot MA, Coppens S, Pedersen JS, Katzman S, King B, Onodera C, Siepel A, Kern AD, Dehay C, Igel H, Ares M Jr, Vanderhaeghen P, Haussler D (2006-08-16). An RNA gene expressed during cortical development evolved rapidly in humans. Nature 443 (7108). supplement
  2. 2.0 2.1 Pollard KS, Salama SR, King B, Kern AD, Dreszer T, Katzman S, Siepel A, Pedersen JS, Bejerano G, Baertsch R, Rosenbloom KR, Kent J, Haussler D (October 2006). Forces shaping the fastest evolving regions in the human genome. PLoS Genet. 2 (10): e168.
  3. HACNS1: Gene enhancer in evolution of human opposable thumb. Science Codex. URL accessed on December 2009.

Further reading[edit | edit source]

External links[edit | edit source]

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