Question

What are the two essential components of the CRISPR gene-editing system that would have to be introduced into a cell in order to target a gene for cleavage?

Answer 1

Cas 9 enzyme and guide CRISPR RNA.

Rationale:

• CRISPR -Clustured Regularly Interspaced Short Palindromic Sequence,is a immune system of many bacteria,archaea that act against the invading viral genomic DNA.

Entry of viral genome-------> Cas 1-2 enzymecomplex acquiring the segment of virus that acts as protospacer----------> Inserted in to CRISPR loci in between repeat sequence---------> Which is transcribed as pre CRISPR RNA-------->Develop as mature guide CRISPR RNA------->cas 9 attaches with guide RNA form complex called guide CRISPR RNA -cas9 complex--------> this complex guides attaches to the target DNA-------> Endonucleolytic cleavage of DNA

• Guide RNA and CRISPR-associated endonuclease (Cas protein) are two important component for a cell to target cleavage of gene.
• This guide CRISPR RNA guides the cas9 protein to target the invading DNA sequence,it recognises with the help of complementarity nature of guide CRISPR RNA with the invading sequence.
• Then the enzyme introduces a double strand break and cleaves the sequences of target DNA.This cleavage leads to destruction of invading sequence so the bacterias are protected from viral infection.
• In the same way it is used for gene editing by researchers.Generally the nicked regions are repaired with the help of Homology directed repair(HDR) mechanism and Non-homologous end joining mechanism(NHEJ)

Hope this helps you:)