We will talk about Genomic and cDNA libraries. What is a library of genome then? Well, the genome is too large for most organisms to handle. Too big to work with or to study. It’s so often better to cut it down into smaller pieces that you can look at.
How can a genomic library be made? Well, we begin with our interest cell. And the first thing we’ll do is to isolate all the DNA from the cell. When we get the DNA, we will use enzymes to cut it into smaller parts. Now, when choosing which restriction enzyme to use, we must take great care.
We want to use an enzyme with enough limitation in the genome to have sufficient pieces in the vector, but not so small that all the genes are cut. Usually, we’re going to use a plasmid for the vector. A plasmid is a standard and easy way to transform a bacterium into foreign DNA. So, with our restrictive enzyme, we’ll cut down our DNA and plasmid. We might even want two different libraries to produce so that we have cuts in different locations using two different restrictive enzymes. After our DNA and our plasmids have been cut, we now must ligate them with DNA ligase.
When the cdNA has been pasted into the plasmid, we will now be ready to actually transform the cdNA into bacteria. There are various ways of doing this. One of the common things is that we use heat-shock, which heats up the bacteria and then cools them down quickly and leads to a few small holes that allow plasmids to be taken on. The ending is thousands of different bacterial cells, all of which are made up of different sections of the DNA.
Working with them is much easier. And this combination forming our genomic library of all these different cells. So this is a library type. A cDNA library is another type of library; the cDNAs library is different from the genomics library, but the cDNA library only looks at the genes expressed in the cell. The genomic library includes the whole genome of the cell. Let’s go about how we’d build a library of cDNA.
We’ll start with is that we start with mRNA isolation. The mRNA is clearly the RNA expressed in the cell. That is ultimately the cell’s proteins. We will then use reverse transcription for creating the version of the RNA in DNA. That’s what we are talking about again like the cDNA. Once we have the cDNA, we have to add restriction sites to their purpose.
Then we can treat cDNA and the plasmids with restriction enzymes. Once they have been cut, once more we can utilize DNA ligases to combine cut plasmids with the cut-down cDNA with the complete plasmid plus cDNA.
So you only want to add restriction sites to the end. Finally, once again, we are able to convert our cells into our cDNA library and to compare them with the difference in protein expressions between two cells, all of whom have different types of cDNA. And cDNA libraries are useful if you want to compare the difference between the protein expressions between two different cells.
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