CRISPR The Gene Editor that Could Change the World
Many people have heard about CRISPR, but very few actually know what it is, how it works, or even what the big deal is. Well scientists have been excited about the CRISPR system for a while and hopefully, even if you aren't a scientist, I can spread some light on why this will be a big deal going forward.
So What Is It?
CRISPR stands for Clustered regularly interspaced short palindromic repeats. Palindromes are sequences that read the same backwards and forward. So for example madam is a palindrome because it spells the same thing backwards in forwards. In DNA, ACDCA would be a palindrome. CRISPR are specifically DNA sequences found in bacteria, and play major part of the bacterial defense system from things such as viruses. So you might be wondering how it does that? Well, each palindromic repeat is followed by DNA that is nonpalindromic. These pieces are foreign DNA from something that tried to invade the bacteria perviously. Think of it like some guy breaks into your house, and you scare him off, but not before taking his necklace as a trophy. These sequences of DNA are transcribed into RNA and then the RNA is used to find compatible DNA. When it matches a piece of DNA the protein called Cas 9 comes along and cuts the DNA, essentially causing the cell to try to repair it. Now, the cell is pretty good at repairing broken DNA, but in the case of a double stranded break it is pretty bad at it. The end result is that the gene no longer codes for the protein correctly, making it essentially useless. Going back to the earlier analogy, imagine the necklace is like the symbol of for a large robbery group in the area. When you see somebody wearing a comparable necklace you call the police (Cas 9), who then throw them in jail.
What Do Bacteria Have To Do With Us?
Okay, so bacteria have a defense mechanism against foreign intruders, don't we all? What makes this so special? Well, what happens if the RNA was not directed at only foreign matter, but any matter? After all, an RNA sequence is just a bunch of nucleic acids in a string. Labs all over the world can make that easily. Besides that, in order to have the system work we would need the Cas 9 protein and some other technical stuff. Well, all of that stuff is still made from DNA, so we would just need a DNA sequence that the cell could use as instructions to make this stuff (i.e. a plasmid). So its pretty easy to make all the stuff in the lab, but you still haven't explained how to use it.
Well, imagine there is this gene we want to get rid of in a cell for one reason or another. We might want to study it, it might not work probably, or just because. Well, a gene is nothing more then a long chain of DNA. Through genome sequencing, we know, with pretty good accuracy, the sequences of almost all the genes in a cell. So, if I wanted to knock out a gene I would just go into a database and select a DNA sequence. But I have to be careful, because with only 4 possible DNA options and billions of bases making up our DNA we want to make sure nothing overlaps with out chosen sequence. Remember, the DNA will be converted into RNA which will bind to any compatible sequence. So you choose the sequence you want, send it and the other parameters off to a company and then a few days/ weeks later you get a tube of plasmid, which is essentially a piece of DNA that is the blueprints to everything you need. You put that into your cell, and then the cell's machinery does all the rest. Fingers crossed, and in a few weeks you now have cells that do not have the gene of interest.
So I get how it works, but how will it change the world?
I explained how it works on a small scale, but it can work on a larger scale to. Scientists have created mice that are completely missing a gene from all of there cells. This is huge because we could transition this up to humans. Say somebody has a diseased protein that is messing with something important. We can use this system to stop the protein from ever being made. We can revert back to the original function and use the system to fight of viruses, of which humans deal with many of them. Genes are the building blocks of protein, which is THE thing in biology. If we figure out how to edit genes, we can do amazing things. Now, this system has worked great in biology labs but we are still far off using this in humans. Many scientists still have problems with cross reactions, as in the RNA targets non genes of interest, and until this problem is solved it will probably not ever be used in humans.
Sources
1) Biolabs, New England. "CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology." CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology | NEB. N.p., n.d. Web. 04 May 2017.
2) "CRISPR/Cas9 Guide." Addgene. N.p., n.d. Web. 04 May 2017.
3) Ran, F. Ann, Patrick D. Hsu, Jason Wright, Vineeta Agarwala, David A. Scott, and Feng Zhang. "Genome Engineering Using the CRISPR-Cas9 System." Nature Protocols. U.S. National Library of Medicine, Nov. 2013. Web. 04 May 2017.
So What Is It?
CRISPR stands for Clustered regularly interspaced short palindromic repeats. Palindromes are sequences that read the same backwards and forward. So for example madam is a palindrome because it spells the same thing backwards in forwards. In DNA, ACDCA would be a palindrome. CRISPR are specifically DNA sequences found in bacteria, and play major part of the bacterial defense system from things such as viruses. So you might be wondering how it does that? Well, each palindromic repeat is followed by DNA that is nonpalindromic. These pieces are foreign DNA from something that tried to invade the bacteria perviously. Think of it like some guy breaks into your house, and you scare him off, but not before taking his necklace as a trophy. These sequences of DNA are transcribed into RNA and then the RNA is used to find compatible DNA. When it matches a piece of DNA the protein called Cas 9 comes along and cuts the DNA, essentially causing the cell to try to repair it. Now, the cell is pretty good at repairing broken DNA, but in the case of a double stranded break it is pretty bad at it. The end result is that the gene no longer codes for the protein correctly, making it essentially useless. Going back to the earlier analogy, imagine the necklace is like the symbol of for a large robbery group in the area. When you see somebody wearing a comparable necklace you call the police (Cas 9), who then throw them in jail.
What Do Bacteria Have To Do With Us?
Okay, so bacteria have a defense mechanism against foreign intruders, don't we all? What makes this so special? Well, what happens if the RNA was not directed at only foreign matter, but any matter? After all, an RNA sequence is just a bunch of nucleic acids in a string. Labs all over the world can make that easily. Besides that, in order to have the system work we would need the Cas 9 protein and some other technical stuff. Well, all of that stuff is still made from DNA, so we would just need a DNA sequence that the cell could use as instructions to make this stuff (i.e. a plasmid). So its pretty easy to make all the stuff in the lab, but you still haven't explained how to use it.
Well, imagine there is this gene we want to get rid of in a cell for one reason or another. We might want to study it, it might not work probably, or just because. Well, a gene is nothing more then a long chain of DNA. Through genome sequencing, we know, with pretty good accuracy, the sequences of almost all the genes in a cell. So, if I wanted to knock out a gene I would just go into a database and select a DNA sequence. But I have to be careful, because with only 4 possible DNA options and billions of bases making up our DNA we want to make sure nothing overlaps with out chosen sequence. Remember, the DNA will be converted into RNA which will bind to any compatible sequence. So you choose the sequence you want, send it and the other parameters off to a company and then a few days/ weeks later you get a tube of plasmid, which is essentially a piece of DNA that is the blueprints to everything you need. You put that into your cell, and then the cell's machinery does all the rest. Fingers crossed, and in a few weeks you now have cells that do not have the gene of interest.
So I get how it works, but how will it change the world?
I explained how it works on a small scale, but it can work on a larger scale to. Scientists have created mice that are completely missing a gene from all of there cells. This is huge because we could transition this up to humans. Say somebody has a diseased protein that is messing with something important. We can use this system to stop the protein from ever being made. We can revert back to the original function and use the system to fight of viruses, of which humans deal with many of them. Genes are the building blocks of protein, which is THE thing in biology. If we figure out how to edit genes, we can do amazing things. Now, this system has worked great in biology labs but we are still far off using this in humans. Many scientists still have problems with cross reactions, as in the RNA targets non genes of interest, and until this problem is solved it will probably not ever be used in humans.
Sources
1) Biolabs, New England. "CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology." CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology | NEB. N.p., n.d. Web. 04 May 2017.
2) "CRISPR/Cas9 Guide." Addgene. N.p., n.d. Web. 04 May 2017.
3) Ran, F. Ann, Patrick D. Hsu, Jason Wright, Vineeta Agarwala, David A. Scott, and Feng Zhang. "Genome Engineering Using the CRISPR-Cas9 System." Nature Protocols. U.S. National Library of Medicine, Nov. 2013. Web. 04 May 2017.
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