Marraffini · Nature 2015 · narrative review · n=?

CRISPR-Cas immunity in prokaryotes.

Cited 841 times in the scientific literature.

Level 5 - mechanism / opinion, no new human data

Narrative review of basic biological mechanisms (Level 5 by CEBM rules).

PubMed 26432244 · doi:10.1038/nature15386 · record verified 2026-08-26

What was done

This review outlines the molecular mechanism of clustered, regularly interspaced short palindromic repeat (CRISPR)-Cas adaptive immune systems in prokaryotes, summarizing how foreign viral genetic sequences are captured, processed into guide RNAs, and targeted for nuclease cleavage.

What was found

The abstract describes the functional stages of CRISPR immunity qualitatively and contains no numerical data or statistical measures. It details the process wherein host cells integrate a viral genome fragment (spacer) into the CRISPR locus, transcribe it into small RNA guides, and use Cas nucleases to cleave matching viral DNA, establishing vertically heritable resistance across generations.

Why it matters

It provides a foundational synthesis of the natural prokaryotic adaptive immune mechanism that serves as the basis for CRISPR-Cas genome engineering tools.

Limits

The abstract contains no empirical data, sample counts, quantitative metrics, or comparative analyses of specific Cas enzymes or microbial species.

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