What is CRISPR-Cas9?
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments of bacteriophages that had previously infected the prokaryote.
CRISPR gene editing commonly utilizes the cas9 gene. This editing process has a wide variety of applications including basic biological research, development of biotechnology products, and treatment of diseases.
CRISPR is a bacterial immune system that evolved in microbes to allow prevention of viral infection. CRISPR sequences are a crucial component of the immune systems. The immune system is responsible for protecting an organism’s health and well-being. Just like us, bacterial cells can be invaded by small viruses infectious agents. If a viral infection threatens a bacterial cell, the CRISPR immune system can obstruct the attack by destroying the genome of the invading virus.
How does it work?
CRISPR-Cas9 genetic engineering technology enables scientists to change or remove genes quickly and with great precision.
CRISPR are copies of small pieces of viruses. Bacteria use them like collections of mug shots to identify bad viruses. Cas9 is an enzyme that can cut apart DNA. Bacteria fight off viruses by sending the Cas9 enzyme to chop up viruses that have a mug shot in the collection.
The process starts with RNA, a molecule that can read the genetic information in DNA. The RNA finds the spot in the nucleus of a cell where some editing activity should take place. This guide RNA shepherd Cas9 to the precise spot on DNA where a cut is called for.
Then, DNA from an invading virus is processed into short segments that are inserted into the CRISPR sequence as new spacers. CRISPR repeats and spacers in the bacterial DNA undergo transcription, the process of copying DNA into RNA (ribonucleic acid). Unlike the double-chain helix structure of DNA, the resulting RNA is a single-chain molecule. This RNA chain is cut into short pieces called CRISPR RNAs. CRISPR RNAs guide bacterial molecular machinery to destroy the viral material. Because CRISPR RNA sequences are copied from the viral DNA sequences acquired during adaptation, they are exact matches to the viral genome and thus serve as excellent guides.
Discovery of CRISPR-Cas9
Jennifer Doudna, a professor at the University of California-Berkeley, won the Nobel Prize in chemistry for her pioneering research in CRISPR gene editing. She received the prize with Emmanuelle Charpentier of the Max Planck Unit for the Science of Pathogens in Berlin.
Doudna spent years investigating an unusual molecular sequence—acronym, CRISPR—and how it functioned. In 2011 she and microbiologist Emmanuelle Charpentier joined forces in research; the next year, they published revolutionary findings on how CRISPR, combined with an enzyme, Cas9, can cut DNA strands with surgical precision. The result: a gene-editing technique that’s been called the most significant scientific breakthrough of the past century. Now a professor at UC Berkeley, Doudna continues her research and advocates for ethical standards in the use of gene-altering technologies.
Doudna and Charpentier discovered that the CRISPR-Cas9 protein works as genetic scissors, which researchers can use to make changes to the DNA. Their research can contribute to new cancer therapies and represents a major advancement towards curing genetic diseases such as sickle cell disease.
This is a technology that comes from bacteria. It comes from a bacterial immune system that gives bacteria the ability to defend themselves against viruses. Scientists have suggested that Cas9-based gene drives may be capable of editing the genomes of entire populations of organisms. In 2015, Cas9 was used to modify the genome of human embryos for the first time.
Apart from its original function in bacterial immunity, the Cas9 protein has been heavily utilized as a genome engineering tool to induce site-directed double-strand breaks in DNA. These breaks can lead to gene inactivation or the introduction of heterologous genes through non-homologous end-joining and homologous recombination respectively in many laboratory model organisms.
CRISPR is a technology that will be broadly applicable for treating genetic disease in the future as a way to correct the actual genes that lead to disease.
Doudna views on the challenges faced by women
Doudna became the first woman on the UC Berkeley faculty to win a Nobel, and she and Charpentier are the first women to share a Nobel in the sciences.
In a conversation with National Geographic Doudna said that she was never given any particular advantages or disadvantages based on her gender. People want to be valued for who they are as a person and what their contributions are, rather than being given some kind of special dispensation for things that are out of their control according to their birth.
Although she never got any advantages or disadvantages because of her gender, it is the fact that women face this in their daily life. And that has made her much more aware of the importance of being very open about the challenges that women face, the ways that women are viewed in the national and international media, and the way different cultures are portraying women, in their professional roles especially. We need to continue to discuss these issues and ensure that women feel welcome and enabled them to contribute fully to society in whatever way they feel is important to them.
Doudna says, “I’m proud of my gender, ” and she hopes that her win encourages girls and women to pursue their passions and see that their work can be celebrated.
Get to know more about Jennifer Doudna and her discovery:
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