TLS Online TPP Program

#Id: 6783

#Unit 3. Fundamental Processes

cas1, cas2, and cas4 required to create protospacer sequences Cas1 is  integrase, whereas Cas2 is a ribonuclease. In contrast, of other Cas proteins, Cas6 is involved in expression and processing of the CRISPR cluster and Cas3 in the interference of viral infection.

TLS Online TPP Program

#Id: 6784

#Unit 3. Fundamental Processes

The promoter from which expression is initiated is located within the leader region and generates a single RNA transcript called the pre-crRNA.  In the case of E. coli, the CRISPR is associated with eight cas genes, the products of five of which form a complex called Cascade.

TLS Online TPP Program

#Id: 6785

#Unit 3. Fundamental Processes

crRNA and Cascade are then directed to and cleave the target DNA with the help of Cas3 in E.coli

TLS Online TPP Program

#Id: 6786

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6787

#Unit 3. Fundamental Processes

Piwi-associated RNAs, piRNA, are a special class of miRNA found in germ cells have features distinct from miRNAs.  siRNA (small interfering RNA), which is typically produced during a virus infection.

TLS Online TPP Program

#Id: 6788

#Unit 3. Fundamental Processes

Both siRNAs and miRNAs are generated from longer RNA molecules by the enzyme Dicer, an RNase III–like enzyme that recognizes and digests longer dsRNAs or the stem-loop structures formed by miRNA precursors.  The siRNA and miRNA products are typically 21–23 nucleotides long