Grasslands   Grasslands are found on every continent except Antarctica, and cover about 16 per cent of the Earth’s surface.  They develop where there is not enough precipitation to support forests, but enough to prevent deserts forming.

TLS Online TPP Program

#Id: 6781

#Unit 3. Fundamental Processes

A set of conserved protein-coding genes is tightly associated with the CRISPR sequences. The two most highly conserved members (cas1 and cas2, for “CRISPR associated”) are found in all cases

TLS Online TPP Program

#Id: 6782

#Unit 3. Fundamental Processes

The protospacer adjacent motif (or PAM for short) is a short DNA sequence (usually 2-6 base pairs in length) that follows the DNA region targeted for cleavage by the CRISPR system, such as CRISPR-Cas9. The PAM is required for a Cas nuclease to cut and is generally found 3-4 nucleotides downstream from the cut site

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