orthologous

(adjective)

having been separated by a speciation event

Related Terms

Examples of orthologous in the following topics:

  • Homologs, Orthologs, and Paralogs

    • Two segments of DNA can have shared ancestry because of either a speciation event (orthologs) or a duplication event (paralogs).
    • Homologous sequences are orthologous if they were separated by a speciation event: when a species diverges into two separate species, the copies of a single gene in the two resulting species are said to be orthologous.
    • Orthologs, or orthologous genes, are genes in different species that originated by vertical descent from a single gene of the last common ancestor.
    • Orthologous sequences provide useful information in taxonomic classification and phylogenetic studies of organisms.
    • Two organisms that are very closely related are likely to display very similar DNA sequences between two orthologs.

  • Constructing an Animal Phylogenetic Tree

    • Interestingly, 99% of the genes in humans and mice are detectably orthologous, and 50% of our genes are orthologous with those of yeast.
    • The hemoglobin B genes in humans and in mice are orthologous.

  • Size Variation and ORF Contents in Genomes

    • The high numbers of ORFans in bacterial genomes indicate that, with the exception of those species with highly reduced genomes, much of the observed diversity in gene inventories does not result from either the loss of ancestral genes or the transfer from well-characterized organisms (processes that result in a patchy distribution of orthologs but not in unique genes) or from recent duplications (which would likely yield homologs within the same or closely related genome).

  • Quorum Sensing

    • Three-dimensional structures of proteins involved in quorum sensing were first published in 2001, when the crystal structures of three LuxS orthologs were determined by X-ray crystallography.

  • Gene Duplications and Divergence

    • Both orthologous genes (resulting from a speciation event) and paralogous genes (resulting from gene duplication within a population) can be said to display divergent evolution.