Back2Basics: CRISPR-Cas9 Technology

• CRISPR-Cas9 stands for Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9.
• It is a technology that allows geneticists and researchers to edit parts of the genome by altering sections of the DNA sequence.
• Emmanuelle Charpentier and Jennifer Doudna’s work on CRISPR-Cas9 as a ‘molecular scissor’ earned them the 2020 Nobel Prize in chemistry.
• The system consists of two key components:

1. Cas9: This is the enzyme that acts like a pair of molecular scissors. It is responsible for cutting the DNA strand at a specific location, allowing for the removal, addition, or alteration of DNA at that site.
2. Guide RNA (gRNA): This is a piece of RNA that is designed to find and bind to a specific sequence of DNA that matches its code. The gRNA guides the Cas9 enzyme to the exact spot in the genome where an edit is desired.

• Mechanism:
  • The process begins with the design of a gRNA that matches the DNA sequence where an edit is needed.
  • Once inside the cell, the Cas9 enzyme and the gRNA form a complex that can identify and bind to the target DNA sequence.
  • The Cas9 then cuts the DNA at this location.
  • After the DNA is cut, the cell’s natural repair mechanisms can be harnessed to add or remove genetic material, or to make specific changes to the DNA.
• Applications: Used for gene editing to correct genetic disorders, develop targeted cancer therapies, enhance diagnostics for infectious diseases, and create personalized medicine approaches.

TB Situation in India:

• TB kills an estimated 480,000 Indians annually, or over 1,400 patients every day.
• India has more than a million ‘missing’ TB cases each year, which remain undiagnosed or inadequately diagnosed and treated in the private sector.

PYQ:

[2019] What is Cas9 Protein that is often mentioned in news?

(a) A molecular scissors used in targeted gene editing

(b) A biosensor used in the accurate detection of pathogens in patients

(c) A gene that makes plants pest-resistant

(d) A herbicidal substance synthesized in genetically modified crops

[2014] Can overuse and free availability of antibiotics without Doctor’s prescription, be contributors to the emergence of drug-resistant diseases in India? What are the available mechanisms for monitoring and control? Critically discuss the various issues involved.