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Comparing gene function and relationships

  • As well as comparing the order of genes among different organisms, it can be of interest to know whether these genes have a ancestral relationship.
  • The term ortholog is used to denote a gene present in two or more different species, in which all copies have descended from a common ancestral gene (as opposed to paralogs, see next slide). Orthologs may or may not have a similar function in their present species.
  • Historically, homology meant having a common evolutionary origin. However, it is now generally used to describe the extent of similarity between two DNA sequences (to the dismay of many language purists).
  •     Slide 22
    Almost all human disease genes have orthologs in rodent genomes (Huang et al., 2004).
    Slide 22
    image from Wellcome Trust Sanger Institute http://www.sanger.ac.uk/Info/Press/2002/021205.shtml?;decor=printable