Genome editing

Genome editing, or genome editing with engineered nucleases (GEEN) is a type of genetic engineering in which DNA is inserted, deleted or replaced in the genome of a living organism using engineered nucleases, or "molecular scissors." These nucleases create site-specific double-strand breaks (DSBs) at desired locations in the genome. The induced double-strand breaks are repaired through nonhomologous end-joining (NHEJ) or homologous recombination (HR), resulting in targeted mutations ('edits').

As of 2015 there were four families of engineered nucleases being used: meganucleases, zinc finger nucleases (ZFNs), transcription activator-like effector-based nucleases (TALEN), and the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system. The structure of 9 genome editors as of 2017 can be viewed.

Genome editing was selected by Nature Methods as the 2011 Method of the Year. The CRISPR-Cas system was selected by Science as 2015 Breakthrough of the Year.

A common approach in modern biological research is to modify the DNA sequence (genotype) of an organism (or a single cell) and observe the impact of this change on the organism (phenotype). This approach is called reverse genetics and its significance for modern biology lies in its relative simplicity. This method contrasts with that of forward genetics, where a new phenotype is first observed and then its genetic basis is studied. This course is more complex because phenotypic changes are often a result of multiple genetic interactions.

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