pseudogene

Examples of pseudogene in the following topics:

• Genome Evolution

  • Processes such as mutations, duplications, exon shuffling, transposable elements and pseudogenes have contributed to genomic evolution.
  • Often a result of spontaneous mutation, pseudogenes are dysfunctional genes derived from previously functional gene relatives.
  • There are many mechanisms by which a functional gene can become a pseudogene including the deletion or insertion of one or multiple nucleotides.
  • Often cited examples of pseudogenes within the human genome include the once functional olfactory gene families.
  • Over time, many olfactory genes in the human genome became pseudogenes and were no longer able to produce functional proteins, explaining the poor sense of smell humans possess in comparison to their mammalian relatives.

• Bacterial Genomes

  • Free-living bacteria have the largest genomes out of the three types of bacteria; however, they have fewer pseudogenes than bacteria that have recently acquired pathogenicity.
  • Facultative and recently evolved pathogenic bacteria exhibit a smaller genome size than free-living bacteria, yet they have more pseudogenes than any other form of bacteria.
  • Obligate bacterial symbionts or pathogens have the smallest genomes and the fewest number of pseudogenes of the three groups.
  • As such, selection can effectively operate on free-living bacteria to remove deleterious sequences resulting in a relatively small number of pseudogenes.
  • As such, in recently formed and facultative parasites, there is an accumulation of pseudogenes and transposable elements due to a lack of selective pressure against deletions.

• Variations in Size and Number of Genes

  • M.leprae has lost many once-functional genes over time due to the formation of pseudogenes.
  • Thus over time these genes have lost their function through mechanisms such as mutation causing them to become pseudogenes.

• Genome Reduction

  • This model illustrates four general features of reduced genomes and obligate intracellular species: ‘genome streamlining' resulting from relaxed selection on genes that are superfluous in the intracellular environment; a bias towards deletions (rather than insertions), which heavily affects genes that have been disrupted by accumulation of mutations (pseudogenes); very little or no capability for acquiring new DNA; and considerable reduction of effective population size in endosymbiotic populations, particularly in species that rely on vertical transmission.