"I think the thing that's amazing about science and about biology for me is that there is always more to be discovered and every time we feel like we've figured something out, it seems to open up several more questions." - Jennifer Doudna
CRISPR-Cas9 is a powerful gene-editing tool which easily allows scientists to remove and replace particular parts of DNA sequence. The CRISPR-Cas system was originally discovered in bacteria and acts as a defense system against phages and foreign DNA. Jennifer Doudna and Emmanuelle Charpentier discovered that a protein called Cas9 can easily cut desired gene or DNA sequence by combining with specific "guide RNA" (gRNA) which corresponds to the target DNA sequence.
The development of the CRISPR-Cas9 system is very exciting due to its huge application potential in different areas such as gene therapy, agriculture and biofuels. In the past, scientists have to spend a lot of time and effort to remove one particular gene but CRISPR-Cas9 technology enables scientists to remove a specific gene precisely within a short time.
In general, the CRISPR-Cas9 system mainly consists of two components which are the guide RNA and a protein called Cas with endonuclease activity. The guide RNA is made up of a CRISPR-RNA (crRNA) sequence and trans-activating crRNA (trRNA). crRNA contains RNA sequence which is complementary to the target DNA and trRNA interacts with crRNA to form a complex structure (crRNA-trRNA) complex and promote engaging to the Cas9 protein. Once the Cas9-gRNA complex recognizes and binds to its target, the target DNA sequence (which matches up with the gRNA) will be cut by the endonuclease activity of Cas9. As a result, the target sequence was removed and this allows scientists to study functions of gene easily.
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