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Related Concept Videos

Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
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Microbial genome evolution is a highly dynamic process shaped by continual gene gain and loss across species and strains. This genomic flexibility allows microorganisms to adapt rapidly to environmental pressures and interactions with other organisms. Central to understanding this diversity is the distinction between the core and pan genomes.The core genome comprises the genes shared by all sampled strains of a species, representing essential functions needed for fundamental cellular processes.
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While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.
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Advancements in molecular biology have revolutionized the identification and characterization of bacteria, with multiple methods leveraging DNA sequencing for enhanced precision. As sequencing technologies improve and costs decline, these approaches are increasingly used in clinical, environmental, and evolutionary studies.Multilocus Sequence Typing (MLST) examines several housekeeping genes, essential chromosomal genes encoding cellular functions, to distinguish strains. Approximately...
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Impact of small repeat sequences on bacterial genome evolution.

Nicholas Delihas1

  • 1Department of Molecular Genetics and Microbiology, School of Medicine, State University of New York, Stony Brook, NY, USA. nicholas.delihas@stonybrook.edu

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Prokaryotic genomes contain diverse repeat elements like miniature inverted-repeat transposable elements (MITEs) and clustered regularly interspaced short palindromic repeats (CRISPRs). These sequences play multifaceted roles in gene regulation, host-pathogen interactions, and defense mechanisms, influencing genome evolution.

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Area of Science:

  • Genomics
  • Molecular Biology
  • Evolutionary Biology

Background:

  • Prokaryotic genomes feature various repetitive DNA sequences in intergenic regions, including terminal inverted repeats (TIRs), miniature inverted-repeat transposable elements (MITEs), repetitive extragenic palindromic (REP) sequences, and clustered regularly interspaced short palindromic repeats (CRISPRs).
  • The discovery of new repeat elements has accelerated with advancements in whole-genome sequencing, revealing diverse structures and properties.
  • These repeat sequences are not merely non-coding elements; they exhibit functional associations with cellular processes and genetic elements.

Purpose of the Study:

  • To describe the diverse structures, functions, and evolutionary significance of repeat elements found in prokaryotic genomes.
  • To highlight the varied roles these sequences play, from gene regulation to immune defense.
  • To provide an overview of the current understanding of repeat elements in light of extensive genomic data.

Main Methods:

  • Bioinformatic analysis of large-scale whole-genome sequencing data to identify and characterize novel repeat elements.
  • Comparative genomics to study the distribution and evolution of repeat sequences across different prokaryotic species.
  • Functional analysis, including investigation of associations with genes, regulatory elements, and cellular processes.

Main Results:

  • Numerous repeat elements, including MITEs, REP sequences, and CRISPRs, are prevalent in prokaryotic intergenic regions, exhibiting diverse structural features.
  • These repeat sequences demonstrate a wide range of functions, including gene expression control, facilitation of host/pathogen interactions, and involvement in acquired immunity (CRISPRs).
  • Repeat elements are often linked to mobile genetic elements like integrons, can be fused with open reading frames, and influence genomic plasticity and evolution.

Conclusions:

  • Prokaryotic repeat elements are structurally diverse and functionally multifaceted, playing critical roles in cellular processes and evolution.
  • CRISPR systems represent a sophisticated defense mechanism, conferring acquired immunity against foreign genetic elements.
  • The study of repeat elements provides insights into genome evolution, adaptation, and the dynamic nature of prokaryotic genomes.