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head & pubic lice split ~7 Ma?

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  • Marc Verhaegen
    Genome Biol Evol 4(11):1088-1101 doi 10.1093/gbe/evs088 open access Evolution of extensively fragmented mitochondrial genomes in the lice of humans Shao R, Zhu
    Message 1 of 1 , Nov 9, 2012
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      Genome Biol Evol 4(11):1088-1101 doi 10.1093/gbe/evs088 open access
      Evolution of extensively fragmented mitochondrial genomes in the lice of
      humans
      Shao R, Zhu XQ, Barker SC & Herd K 2012

      Bilateral animals are featured by an extremely compact mitochondrial (mt)
      genome with 37 genes on a single circular chromosome.
      The human body louse Pediculus humanus, however, has its mt genes on 20
      mini-chromosomes.

      We sequenced the mt genomes of 2 other human lice:
      - the head louse Pediculus capitis &
      - the pubic louse Pthirus pubis.
      Comparison among the 3 human lice revealed the presence of fragmented mt
      genomes in their LCA ~7 Ma.

      The head louse has exactly the same set of mt mini-chromosomes as the body
      louse:
      the number of mini-chromosomes & the gene content & gene arrangement in
      each mini-chromosome have remained unchanged since the body louse evolved
      from the head louse ~107 ka.

      The pubic louse has the same pattern of one protein-coding or rRNA gene
      per mini-chromosome (except 1 mini-chromosome with 2 protein-coding genes,
      atp6 & atp8) as the head louse & the body louse.
      This pattern is apparently ancestral to all human lice, and has been
      stable for at least 7 Ma.
      Most tRNA genes of the pubic louse, however, are on different
      mini-chromosomes when compared with their counterparts in the head louse &
      the body louse.
      It is evident that re-arrangement of 4 tRNA genes (for leucine, arginine,
      glycine) was due to gene-identity switch by point mutation at the 3d
      anti-codon position or by homologous recombination ;
      re-arrangement of other tRNA genes was by gene translocation between
      mini-chromosomes, likely caused by mini-chromosome split via gene
      degeneration & deletion.

      _____

      This might suggest that the hominid LCA (Gorilla-Homo-Pan) ~7 Ma had head
      separate hairs & pubic hairs, IOW, had a naked body.

      --marc
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