How Genome Editing technology CRISPR is revolutionizing medical research!
CRISPR is a revolutionary and emerging genome editing technology. CRISPR stands for “Clustered Regulatory Interspaced Shot Palindromic Repeats”. This technique allows highly distinctive and rapid modification of DNA in genome which has high degree of flexibility and accuracy.
CRISPR are small segments of genetic code with a specific format. They contain palindromic sequence which shows up over and over again. A palindromic sequence (palindromes) is a series of characters which can be read same forward and backward. See image below for some sample palindromic words. They are common in DNA. Some of these DNA palindromes act as backups for damage to the genetic code, while others are common in cancer mutations.
CRISPR is a bacterial immune system that allows them to detect virus and destroy them. Cas 9 is a protein of CRISPR system which possess ability to cut DNA and eventually degrade viral DNA. When a virus infects a cell, they inject their DNA.
When a virus infects a bacterial cell, they inject their DNA. The CRISPR system of bacterial cell allows to remove the viral DNA and insert it in form of small segments into its own DNA. The site at which these segments are inserted is called as CRISPR. It’s a mechanism that allows the cell to keep record of the viruses they have been exposed to. Also, these segments of DNA are passed on to the cell’s progeny, so bacteria are protected from the virus for many generations of cells.
Once the segments or bits of DNA are inserted into bacterial chromosome, the cell then makes little copy of a molecule called RNA, that is an exact replicate of the viral DNA. RNA is a chemical cousin of DNA and it allows interaction with DNA molecules with the matching sequence.
The little segments of RNA from the CRISPR locus connects and then bind to the protein called Cas9, and form a complex that functions like a guard in the cell. It searches through all of the DNA in the cell, to find sites that match the sequences in the RNA. And when those sites are found the complex links with the DNA and allows the Cas9 cleaver to cut the viral DNA. It makes very precise break.
The Cas9 RNA guard complex acts like a pair of scissors in this process. It makes a double stranded break in the DNA helix. And this complex is programmable, so it can be programmed to recognize particular DNA sequence, and double-stranded break is created in DNA at specific site. This activity can be utilized for genome engineering, to allow cell to make a very precise change to the DNA, at the site where this break was introduced.
The cells have ability to detect broken DNA and repair it. So, when a plant or an animal cell detects a double-stranded break in its DNA, it can fix the break. It is done either by pasting together the ends of the broken DNA with a little or tiny change in sequence of that position, or it can repair the break by merging a new piece of DNA at the site of cut.
When a double stranded break is introduced in DNA at precise places, it can trigger cells to repair those breaks, by either deleting or adding new genetic information. So, once a double-stranded break is made in DNA, repair can be induced, and thereby potentially achieve amazing things, like being able to correct mutation that leads to sickle cell anemia or Tay-Sachs’s disease, or phenylketonuria or Huntington disease.
CRISPR technology have the potential to transform medicine, enabling us not only to treat but also prevent many diseases. This technology can be used to make a very precise changes that can allow to study the changes in the cell’s DNA.
