•  Clustered regularly interspaced short palindromic repeats(CRISPR, pronounced crisper) are segments of prokaryotic DNA containing short, repetitive base sequences.
•  In a palindromicrepeat, the sequence of nucleotides is the same in both directions. Each repetition is followed by short segments of spacer DNA from previous exposures to foreign DNA (e.g., a virus or plasmid). Small clusters of cas (CRISPR-associated system) genes are located next to CRISPR sequences.
•  The CRISPR/Cas system is a prokaryotic immune systemthat confers resistance to foreign genetic elements such as those present within plasmids and phages that provides a form of acquired immunity.

Applications:-

Genome engineering

CRISPR/Cas9 genome editing is carried out with a Type II CRISPR system. When utilized for genome editing, this system includes Cas9, crRNA, tracrRNA along with an optional section of DNA repair template that is utilized in either Non-Homologous End Joining (NHEJ) or Homology Directed Repair (HDR).

Major components

Knockdown/activation

Using “dead” versions of Cas9 (dCas9) eliminates CRISPR’s DNA-cutting ability, while preserving its ability to target desirable sequences. Multiple groups added various regulatory factors to dCas9s, enabling them to turn almost any gene on or off or adjust its level of activity.

• Disease model

CRISPR simplifies creation of animals for research that mimic disease or show what happens when a gene is knocked down or mutated. CRISPR may be used at the germline level to create animals where the gene is changed everywhere, or it may be targeted at non-germline cells

·        Biomedicine

CRISPR/Cas-based “RNA-guided nucleases” can be used to target virulence factors, genes encoding antibiotic resistance and other medically relevant sequences of interest. This technology thus represents a novel form of antimicrobial therapy and a strategy by which to manipulate bacterial populations.

RNA editing

HIV and polio viruses encode genetic information in RNA rather than DNA. Certain bacteria through CRISPR can dismember such viruse’s RNA eventually destroying them.

Concern against CRISPR
1) Pro-life vs Pro-choice debate- warning of possible disorders in foetuses sparks the debate of whether to abort such a foetus.
2) Womb level doping- for desirable athletic endurance, hyper-intelligence etc.
3) Mosaicism- CRISPR led gene correction can sometimes lead to alteration of nearby genes as well.
4) Risk factor- Committee on Human Genome Editing reports suggest CRISPR to be too risky for use on humans.

Conclusion:-

This CRISPR technology is indeed a path-breaking technology, to alter genes in order to tackle a number of conventional and unconventional problems, especially in the health sector. However, experiments and tests to validate its use must be subjected to appropriate scrutiny by the regulators, and their use must be controlled to prevent commercial misuse.