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Selection on the genic location of disruptive elements.

M W J van Passel1, H Ochman

  • 1Department of Biochemistry and Molecular Biophysics, University of Arizona, 1007 East Lowell Street, Tucson, AZ 85721, USA. mvpassel@email.arizona.edu

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Microbial genomes avoid placing long, disruptive mononucleotide repeats within genes. This pattern minimizes the negative impacts of mutations in coding DNA, suggesting selection acts beyond neutral evolution for pseudogenes.

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Area of Science:

  • Microbial genomics and molecular evolution.
  • DNA sequence analysis and bioinformatics.

Background:

  • Nucleotide patterns in prokaryotic coding regions are shaped by selection for DNA/RNA stability and translational accuracy.
  • Mononucleotide repeats are known to be mutagenic and can disrupt gene function.

Purpose of the Study:

  • To investigate the positional bias of mononucleotide repeats within microbial genes.
  • To determine if the length of these repeats influences their location.

Main Methods:

  • Analysis of nucleotide patterns in coding regions of microbial genomes.
  • Identification and positional mapping of mononucleotide repeats of varying lengths.

Main Results:

  • A pervasive bias in the location of mononucleotide repeats within microbial genes was detected.
  • This bias becomes more pronounced with increasing repeat length.
  • The observed pattern suggests a mechanism to minimize the impact of these mutagenic elements.

Conclusions:

  • The non-random distribution of mononucleotide repeats indicates selection against their presence in functional coding regions.
  • This pattern supports the hypothesis that minimizing the costs of transcribing and translating nonfunctional genes is a significant evolutionary pressure.
  • Pseudogene evolution may be influenced by selection pressures beyond strict neutrality.