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Animal Mitochondrial Genetics02:59

Animal Mitochondrial Genetics

Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...
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Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing
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Nonadaptive evolution of mitochondrial genome size.

Bastien Boussau1, Jeremy M Brown, Matthew K Fujita

  • 1Department of Integrative Biology, University of California-Berkeley, 3060 Valley Life Sciences Building, Berkeley, California, 94720-3140, USA. bastien.boussau@univ-lyon1.fr

Evolution; International Journal of Organic Evolution
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Genome size variation in tetrapods may arise from nonadaptive processes. Recent gene duplications in geckos and frogs coincided with reduced natural selection, suggesting genome complexity can evolve without direct benefit.

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Area of Science:

  • Evolutionary Biology
  • Genomics
  • Molecular Evolution

Background:

  • Genome size and complexity exhibit significant variation across species, driven by evolutionary forces.
  • A hypothesis suggests genome size increases are deleterious, linked to reduced population sizes, but this is debated.
  • Previous analyses supporting this were confounded by phylogenetic nonindependence.

Purpose of the Study:

  • To investigate the role of nonadaptive processes in genome size evolution.
  • To test the hypothesis that genome expansions are deleterious by examining sequence evolution after duplication fixation.
  • To analyze mitochondrial genomes in geckos and frogs for evidence of selection efficiency changes.

Main Methods:

  • Comparative genomic analysis of mitochondrial genomes.
  • Studied independent clades of Heteronotia binoei geckos and mantellid frogs.
  • Assessed changes in the efficacy of purifying selection following gene duplication events.

Main Results:

  • Fixation of gene duplications in gecko and frog mitochondrial genomes was observed.
  • These duplication events coincided with a decreased ability of natural selection to remove slightly deleterious mutations.
  • Evidence suggests genome complexity can increase through nonadaptive mechanisms in tetrapods.

Conclusions:

  • The study supports the idea that genome complexity can evolve via nonadaptive processes in tetrapods.
  • Genome size evolution may not solely be driven by adaptive changes or linked to population size fluctuations.
  • Nonadaptive processes, such as relaxed selection after duplication, can contribute to genome evolution.