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technology:dna-editing
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Table of Contents
CRISPR Cas9
Cas 9 enzyme has a sequence locator called the PAM. When the PAM finds a piece of DNA with its sequence, the enzyme unzips the adjacent DNA to see if it matches the guide-RNA. Matching DNA triggers the Cas 9 enzyme to double-strand-break (DSB) the DNA. A DSB is often not a clean break. Some nucleotides can be lost in the process.
The host DNA repair mechanisms come about to repair the DSB, and if a homologous DNA strand is around, it will be used as a template for repair. The homologous DNA can be provided as part of the technological payload, for the purpose of altering the genome.
Zinc Finger
TALENS
Meganucleases
Site Specific Recombinases SSRs
“Relying on homology-directed-repair (HDR) for editing risks introducing indels or chromosomal translocations. Even with a precisely targeted nuclease, with HDR, “you’re at the mercy of the cell,” Stoddard observes. For editing without the unpredictability of HDR, he adds, watch for developments in site-specific recombinases (SSRs).” (Tachibana 2019)1)
However, it can take 100 days to prepare an SSR, whereas CRISPR Cas9 takes one day, so it is speedier for research.
technology/dna-editing.1575702358.txt.gz · Last modified: 2019/12/07 07:05 by marcos
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