Question

4. What is CRISPR? Describe the mechanism in detail with respect to bacterial resistance to phage. Following this, go on to briefly describe why this is rapidly becoming useful DNA technology. What are the ethical implications of this? 5. What is quorum sensing? What are the evolutionary costs and benefits of this process? Describe one known occurrence of quorum sensing in nature.

Answer 1

CRISPR / cas q systems 'GENE EDITING shost alandromi intacpaced clustered regulary Repeats. o DNA sequences in bacteria and archaca snippets of DNA from viruses detect and distory DNA rom similar • small clusters of cas (CRISPR-associated genes are located next to CRISPR sequences) • RNA harboring the spacer sequence helps cas (LRISPR-associated ) proteins recognise and cut exogenous DNA cas q is niecdease complesed with a synthetic guide RNA (guide RNA) can be catat a desired location . Streptococcus (Type II) CRISPR repeat spacer array - cas genes leader dsDNA I repeat Spacer General Mechanism: 1) 2) 3) Adaptation phase Expression. I maturation phase Interference phase.

Protospaces wraldobna Cast- Casa complen protospocer phase I I prowapacer entegration Host datna Leader adoptation CRISPR repeat spacer array 1 Transcription - preoRNA phase . depression Aud Maturation R_I_1- 11-23 . Cas complex & Processing - herRNA (ORNA CAS RNP complex phase. endameleolytic clevage tat protospaun Therference

applications of CRISPR :

1. Easy to generate by simple molecular cloning technique .

2. high target efficiency

3.ability to multiplex for multiple targeting of genes.

ANS 2: 1. Quorum sensing: The bacterial communication phenomenon that allows the bacteria to communicate using secreted signal molecules to assess their population density.

2. quorum sensing is the regulation of gene expression in response to fluctuations in cell - population density 3.research on how V. fischeri regulates bioluminescence led to discovery of bacterial qurom sensing via N-acyl L-homoserine lactones . when the cell density increases the AHL increases which in turn helps out in bioluminesccence.