Understanding The New Powerful Technology- Crispr Cas9

Posted by GAIRIKA BHATTACHARYA on Mon, Sep 12, 2016  
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A revolutionary technology CRISPR-Cas9 is the talk of the scientific world at the moment. It is being considered as a revolutionary technology that will finally help scientists to edit and transform the genome! Over the years scientists all over the world have been employing different technologies to introduce changes in particular regions in the genome but, the CRISPR-Cas9 is a faster and cheaper way of genome editing.


Scientists have already used CRISPR to rectify genetic defects like muscular dystrophy, hepatitis and cystic fibrosis in animal models. However, an application on human germ line cells is not happening soon. The CRISPR is a technique which has evolved in bacteria to fight against viral infections.


The CRISPR-Cas9 has 2 main components: a guide RNA (gRNA) component that guides the Cas9 to particular place on the genome where the nucleotides would be cut. It has bases which are complementary to bases in the target genome region which helps in its effective binding; a Cas9 scalpel that acts like a pair of scissors used to cut the two DNA strands and remove the nucleotides from the specified position.


How does it work?

  1. When a virus attacks a bacterium, the latter captures a segment of the virus’s DNA sequence and stores it.
  2. On a second attack by the virus, the bacterium will create a copy of guide RNA which will find out the complementary target sequence in the genome of the virus.
  3. The guide RNA recruits the scalpel Cas9 and together the CRISPR-Cas9 will scan the viral genome for a marker sequence which matches the sequence stored in the bacterium’s memory.
  4. Once found, the CRISPR-Cas9 will unwind the strand, cut the DNA sequence and degrade it thereby, preventing its reproduction.
  5. The cut around the site will be repaired.


Scientists have therefore devised a plan to use this CRISPR-Cas9 technology to remove defective gene sequences that may affect the health of plants or animals. This technology can be used to create drought resistant crops, to introduce disease resistant genes or to treat severe human diseases like AIDS.


This technology can also be used to treat the problem of donor shortage. It has been known since long that the organs of pigs are almost similar to that of humans but, the former’s genome contains PERV virus (which resemble the virus that causes AIDS in humans).


Researchers are using this technology to edit the pig genome and remove the PERV genes and then mix them with human cells in the laboratory. It has been reported that none of the human cells got infected thereby reinforcing the fact the after proper gene editing pig organs can be used to treat the problem of human organ donor shortage. Similarly, this technique is also being used to remove the gene causing dengue from Ae. aegypti mosquito and replace it with a gene that would make the offspring sterile. This process if successful will help in reducing the number of deaths that occur every year due to malaria or dengue, predominantly in the African continent. The world needs to gain maximum benefit from this potential revolution.


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