CRISPR-Cas9 & Genome editing Explained

CRISPR stands for “Clustered Regularly Interspaced Short Palindromic Repeats“.

I’m pretty sure that you all heard about this buzzword “CRISPR” already. And if not, you are at the right place to get some brief introduction about this new revolution in the biotech world.

Scientists are doing genome or genetic engineering from decades with fundamental rDNA technology. But from the year 2013, everything has changed.

World leading biochemist & geneticist, Jennifer Doudna with the support of colleagues developed an amazing and highly rated technique which we know as CRISPR-Cas9 technique.

What is CRISPR-Cas9?

CRISPR-Cas9 is a genome engineering technology that enables scientists to edit parts of the genome by adding, removing or altering particular sections of the DNA sequence.

How CRISPR lets us edit our DNA

How was CRISPR developed?

  • CRISPR-Cas9 was adapted from a naturally occurring genome editing system in the bacteria. The bacteria capture sequences of DNA from bacteriophage (bacteria-attacking viruses) and use them to create DNA segments called CRISPR arrays.
  • These arrays allow the bacteria to target the virus’s DNA, if similar virus attacks again in future or in their next progenies. The bacteria then use Cas9 (an enzyme) to cut that DNA apart, which ultimately disables that invading virus.

How do CRISPR works?

CRISPR Cas9 system
CRISPR Cas9 system
  • The CRISPR system consists of an enzyme known as Cas9 and a piece of RNA called guide RNA (gRNA) which introduce a change or mutation into DNA.
  • Enzyme Cas9 acts as the molecular scissors that can cut the two strands of DNA at a specific location in the genome so that genes can then be added or removed.
  • gRNA or guide RNA consists of the small piece of pre-designed RNA (around 20 bases long) located within a longer sequence of RNA scaffold.
  • Then longer RNA part binds to DNA and the pre-designed RNA sequence guides Cas9 enzyme to the right location of the genome. This mechanism makes sure that the Cas9 protein cuts the desired region in the genome.

gRNA is pre-designed to find that particular sequence in the DNA and ultimately to bind it. The guide RNA has complementary nitrogenous base pairs to those of the target DNA sequence in the genome which means theoretically, this gRNA will bind only to the target sequence of the genome.

  • The protein Cas9 follows gRNA to that same location in the genome sequence and makes a cut across both strands of DNA as we know this enzyme acts as “molecular scissors”.

Naturally, cell recognises that the DNA is damaged and ultimately its repairing system gets active.

That’s how researchers can use this DNA repair system to introduce changes to one or more genes in the genome of the interested cell.


This genome engineering tool comes with a lot of potentials, as this tool revolutionized biotechnology.

But we know, technology has both positives and negatives. It can be used for both for its better and its worse.

Scientists can use this technology for the medical treatment of deadly genetic disorders. And on the other side of it, a bioterrorist can use it to engineer the deadly viruses.

Here we gonna take a look at its amazing applications and potential.

CRISPR Applications

Designer Babies by gene manipulation
Designer Babies
  1. As you have read earlier CRISPR-Cas9 can be used to treat deadly genetic disorders. CRISPR-Cas9 is revolutionizing the way we do Cancer research.
  2. CRISPR can be used to understand the living organisms better as we can edit even single base pair by using this technology.
    Now we can better understand the function of a particular gene and how it interacts with other genes to make a phenotype either by deleting a particular gene or adding a new one.
  3. CRISPR applications involve germline (germ cells) editing but it falls under the realm of ethics as we know it can be used to treat the hereditary disease to give pain-free life to a newborn child but it can also be used for so-called “designer babies“.
  4. We all have heard about recent Chinese experiment secretly ran by Dr He Jiankui, who used CRISPR-Cas9 technique to alter CCR5 gene to prevent entry of HIV virus in the whole life span of Lulu and Nana (those Chinese twins). But at the same time, they got susceptible to other invading microbial and viral attacks.

We should better understand our genome first and then with Scientists & public engagements we all can decide how to apply this amazing technology for the next chapter of Humanity. As a whole, we successfully entered the era of “Bio-century”.

just bunch of cells studying cells🔬📒


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