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CRISPR/Cas9 Genome Editing01:28

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The CRISPR-Cas system serves as a bacterial defense mechanism against invading genetic elements such as viruses and plasmids, forming the foundation for its adaptation as a powerful genome-editing tool. Originally discovered in prokaryotes, this system has been repurposed to revolutionize genetic engineering across a wide range of organisms, including plants, animals, and humans. The core component, Cas9, is an endonuclease derived from Streptococcus pyogenes, capable of introducing...
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Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect themselves. Clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR-Cas) are present in more than 45% of known bacteria and 90% of known archaea.
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Genome editing technologies allow scientists to modify an organism’s DNA via the addition, removal, or rearrangement of genetic material at specific genomic locations. These types of techniques could potentially be used to cure genetic disorders such as hemophilia and sickle cell anemia. One popular and widely used DNA-editing research tool that could lead to safe and effective cures for genetic disorders is the CRISPR-Cas9 system. CRISPR-Cas9 stands for Clustered Regularly Interspaced...
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CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats is a adaptive immune system found in bacteria and archaea that protects against viral infections. This system enables prokaryotic cells to identify, remember, and neutralize foreign genetic elements, primarily bacteriophages, by storing fragments of the invader’s DNA as a genetic memory.The CRISPR immune response begins during an initial infection. Cas (CRISPR-associated) proteins play a central role in this...
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The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
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Updated: Oct 25, 2025

Substrate Generation for Endonucleases of CRISPR/Cas Systems
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CRISPR-Cas Toxin-Antitoxin Systems: Selfishness as a Constructive Evolutionary Force.

Scott William Roy1

  • 1San Francisco State University, San Francisco, CA, USA.

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Researchers discovered a new RNA-based system that makes cells dependent on a specific genetic element. This finding suggests selfish genetic elements may drive the evolution of biological complexity.

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Area of Science:

  • Molecular Biology
  • Genetics
  • Evolutionary Biology

Background:

  • Toxin-antitoxin systems are genetic elements that can influence bacterial populations.
  • The role of selfish genetic elements in driving evolutionary innovation is an area of active research.

Purpose of the Study:

  • To report the discovery and characterization of a novel RNA-based Cas-dependent toxin-antitoxin system.
  • To explore the potential implications of such 'addiction' systems for stabilizing genomic features and driving biological complexity.

Main Methods:

  • Utilized CRISPR-Cas technology to identify and study the RNA-based system.
  • Conducted experiments to demonstrate the 'addiction' phenotype in cells harboring the system.

Main Results:

  • Identified a novel RNA-based system dependent on Cas proteins.
  • Demonstrated that this system 'addicts' cells to the presence of the genetic cassette.
  • Showcased the potential of broadly-defined addiction systems to stabilize diverse genomic features.

Conclusions:

  • Novel RNA-based Cas-dependent addiction systems represent a new class of mobile genetic elements.
  • These systems may play a significant role in genome evolution and the development of biological complexity.
  • Intragenomic conflict driven by selfish elements could be a key factor in evolutionary innovation.