CRISPR is found predominantly in archaeal and bacterial genomes.
Distribution of CRISPR Systems
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated Cas (CRISPR-associated) genes form a powerful adaptive immune system in prokaryotes. These systems provide defense against invading viruses and plasmids. Here's a breakdown of where they are found:
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Archaea: CRISPR sequences are present in nearly all archaeal genomes. This widespread presence highlights the importance of CRISPR in the survival and evolution of archaea.
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Bacteria: Approximately half of all bacterial genomes contain CRISPR sequences. While not as ubiquitous as in archaea, the prevalence is still significant, demonstrating its crucial role in bacterial immunity.
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Eukaryotes: As of now, CRISPR systems have not been naturally found in any eukaryotic genome. While CRISPR technology is heavily used in eukaryotic research and gene editing, the system itself originates from prokaryotes and has been adapted for use in eukaryotes.
Summary
CRISPR is a prokaryotic defense mechanism that is almost universally found in archaea and present in a significant portion of bacteria. It is not naturally occurring in eukaryotes.
