French-American duo Emmanuelle Charpentier and Jennifer Doudna have been awarded the 2020 Nobel Prize for the chemistry of CRISPR, which allows scientists to ‘cut-paste’ inside a genetic sequence.

Try this PYQ:

Q.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

The CRISPR technology

• The CRISPR is an acronym for Clustered Regularly Interspaced Short Palindromic Repeats, developed in the year 2012
• CRISPR has made gene editing very easy and simple, and at the same time extremely efficient.
• The technology works in a simple way — it locates the specific area in the genetic sequence which has been diagnosed to be the cause of the problem, cuts it out, and replaces it with a new and correct sequence that no longer causes the problem.
• The technology replicates a natural defence mechanism in some bacteria that use a similar method to protect itself from virus attacks.

Working of CRISPR

• An RNA molecule is programmed to locate the particular problematic sequence on the DNA strand.
• A special protein called Cas9, often described in popular literature as ‘genetic scissor’, is used to break and remove the problematic sequence.
• A DNA strand, when broken, has a natural tendency to repair itself. But the auto-repair mechanism can lead to the re-growth of a problematic sequence.
• Scientists intervene during this auto-repair process by supplying the desired sequence of genetic codes, which replaces the original sequence.
• It is like cutting a portion of a long zipper somewhere in between and replacing that portion with a fresh segment.
• Because the entire process is programmable, it has a remarkable efficiency and has already brought almost miraculous results.

Uses of CRISPR

• There are a whole lot of diseases and disorders, including some forms of cancer, that are caused by an undesired genetic mutation.
• These can all be fixed with this technology. There are vast applications elsewhere as well. Genetic sequences of disease-causing organisms can be altered to make them ineffective.
• Genes of plants can be edited to make them withstand pests, or improve their tolerance to drought or temperature.

Ethical concerns

• In November 2018, a Chinese researcher in Shenzen created an international sensation with his claim that he had altered the genes of a human embryo that eventually resulted in the birth of twin baby girls.
• This was the first documented case of a ‘designer babies’ being produced using the new gene-editing tools like CRISPR.
• What made matters worse was that the gene-editing was probably done without any regulatory permission or oversight.

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