CRISPR-Cas9 system
CRISPR-Cas9 is a system found naturally in bacteria. Bacteria use it as an adaptive immune
system. Like any bacteriophage, these are the viruses that can infect bacteria. If a bacteriophage
has infected a bacterium for the first time, then bacteria will take some time to degrade the
bacteriophage's genome. But if the same bacteriophage infects the same bacterium again, then
this bacterium will degrade the bacteriophage's genome more quickly and more effectively. This
is called adaptive immune response. Because now this bacterium recognizes this bacteriophage's
genome. So if this bacteriophage attacks this bacterium again, then bacteria will quickly degrade
its genome. So how does bacteria develop this adaptive immune system? In the genome of
bacteria, some repeated sequences are found in the form of clusters. These repeated sequences
are called CRISPR sequence or CRISPR locus. The full form of CRISPR is Clustered Regularly
Interspaced Short Palindromic Repeats. These sequences are found in the form of clusters in the
genome of bacteria. These clusters are regular. And it is interspaced. Space is found between the
CRISPR arrays. They are short, 30 to 34 nucleotides long.They are palindromic. That is, you
read it in this direction or in this direction. If we talk about direction, then the direction of DNA
is the same. But if you read on both strands of DNA, then it will give you the same read. Read
the upper strand like this and read the lower strand like this. Direction is same 5 to 3, 5 to 3.So it
will give us the same read. So it is a palindromic repeat. You see, it is repeating back to back. So
the sequences found in the genome of bacteria are these. Upstream of these sequences, the CA’s
gene is found here.That is, the gene that makes the Cas protein. And this protein behaves as an
enzyme. So first of all, when bacteriophage infects the bacteria, First of all, Cas1 and Cas2
proteins are synthesized. These are two different proteins, but they work together. This protein
recognizes the genome of bacteriophage. When this protein recognizes the genome, then it is not
that it can bind randomly anywhere in the genome. It binds to a specific location in the genome
of bacteriophage. And we call that location, that site, PAM site. Here it is called PAM site. This
PAM site is recognized by Cas1 and Cas2 proteins. The full form of PAM is Protospacer
Adjacent Motif, PAM.If we talk about the sequence of these PAM sites, then it is NGG.N can be
any nucleotide, followed by guanine and guanine. So NGG, there are a lot of chances that two
guanines can be found in the genome of bacteriophage. So N can be any nucleotide. So NGG, the
Protospacer sequence, is found in the genome of bacteriophage at multiple locations. If this is the
PAM site, then the region found upstream of it is called the Protospacer region.PAM site is
recognized by Cas1 and Cas2 proteins. After recognizing, these two proteins bind here.And after
binding, this protein cuts the double strand of DNA.And in this way, the upstream region of the
PAM site, which we are calling the Protospacer region, cuts that Protospacer region. After that,
this Protospacer region is incorporated in DNA toward 5' end. This is the side of DNA's 5' end.
So it is incorporated towards 5' end in Danaher, this integration work is also done by Cas
proteins. And as soon as it is integrated here, again a CRISPR arrays synthesized here.So after
that, the first step is called Spacer acquisition.Because here, this Protospacer region acquired this
Spacer region.So Spacer acquisition.After Spacer integration, this CRISPR array transcribes the
RNA polymerase enzyme.The bacterial RNA polymerase enzyme, the same RNA polymerase
enzyme participates here.And this CRISPR array is transcribed to make RNA.So this becomes
CRISPR-Cas9 is a system found naturally in bacteria. Bacteria use it as an adaptive immune
system. Like any bacteriophage, these are the viruses that can infect bacteria. If a bacteriophage
has infected a bacterium for the first time, then bacteria will take some time to degrade the
bacteriophage's genome. But if the same bacteriophage infects the same bacterium again, then
this bacterium will degrade the bacteriophage's genome more quickly and more effectively. This
is called adaptive immune response. Because now this bacterium recognizes this bacteriophage's
genome. So if this bacteriophage attacks this bacterium again, then bacteria will quickly degrade
its genome. So how does bacteria develop this adaptive immune system? In the genome of
bacteria, some repeated sequences are found in the form of clusters. These repeated sequences
are called CRISPR sequence or CRISPR locus. The full form of CRISPR is Clustered Regularly
Interspaced Short Palindromic Repeats. These sequences are found in the form of clusters in the
genome of bacteria. These clusters are regular. And it is interspaced. Space is found between the
CRISPR arrays. They are short, 30 to 34 nucleotides long.They are palindromic. That is, you
read it in this direction or in this direction. If we talk about direction, then the direction of DNA
is the same. But if you read on both strands of DNA, then it will give you the same read. Read
the upper strand like this and read the lower strand like this. Direction is same 5 to 3, 5 to 3.So it
will give us the same read. So it is a palindromic repeat. You see, it is repeating back to back. So
the sequences found in the genome of bacteria are these. Upstream of these sequences, the CA’s
gene is found here.That is, the gene that makes the Cas protein. And this protein behaves as an
enzyme. So first of all, when bacteriophage infects the bacteria, First of all, Cas1 and Cas2
proteins are synthesized. These are two different proteins, but they work together. This protein
recognizes the genome of bacteriophage. When this protein recognizes the genome, then it is not
that it can bind randomly anywhere in the genome. It binds to a specific location in the genome
of bacteriophage. And we call that location, that site, PAM site. Here it is called PAM site. This
PAM site is recognized by Cas1 and Cas2 proteins. The full form of PAM is Protospacer
Adjacent Motif, PAM.If we talk about the sequence of these PAM sites, then it is NGG.N can be
any nucleotide, followed by guanine and guanine. So NGG, there are a lot of chances that two
guanines can be found in the genome of bacteriophage. So N can be any nucleotide. So NGG, the
Protospacer sequence, is found in the genome of bacteriophage at multiple locations. If this is the
PAM site, then the region found upstream of it is called the Protospacer region.PAM site is
recognized by Cas1 and Cas2 proteins. After recognizing, these two proteins bind here.And after
binding, this protein cuts the double strand of DNA.And in this way, the upstream region of the
PAM site, which we are calling the Protospacer region, cuts that Protospacer region. After that,
this Protospacer region is incorporated in DNA toward 5' end. This is the side of DNA's 5' end.
So it is incorporated towards 5' end in Danaher, this integration work is also done by Cas
proteins. And as soon as it is integrated here, again a CRISPR arrays synthesized here.So after
that, the first step is called Spacer acquisition.Because here, this Protospacer region acquired this
Spacer region.So Spacer acquisition.After Spacer integration, this CRISPR array transcribes the
RNA polymerase enzyme.The bacterial RNA polymerase enzyme, the same RNA polymerase
enzyme participates here.And this CRISPR array is transcribed to make RNA.So this becomes
