CONTENTSGenomic library .......................... pg 2

DNA library ......................... pg 3

Genomic lib (intro) .................... pg 4

Steps involved ....................... pg 5-6

Probe ....................... pg 7

Probe (diagrams) ......................... pg 8-9

PCR ........................... pg 10

Pcr (intro) ........................... pg 11

Pcr invention ............................. pg 12

Components ............................. pg 13-14

Working ......................... pg 15

Denaturation ........................ pg 16

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Annealing ..................... pg 17

Elongation ..................... pg 18

Review ..................... pg 19

Advantage &

Disadvantage ..................... pg 20

Conclusion ...................... pg 21

Blank page ...................... pg 22

Glossry ...................... pg 23

Sources ....................... pg 24

End ........................ pg 25

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GENOMIC LIBRARY

What are DNA libraries?

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A DNA library is a collection of clones of DNA designed so that there is a high probility of finding any particular piece of the source DNA in the collection.

What are the types of DNA libraries?

The two types o DNA libraries are:

1. GENOMIC LIBRARY:

The genomic library contains DNA fragments representing entire genome of an organism.

2. cDNA LIBRARY:

The cDNA library contains only complementry DNA molecules synthesized from mRNA molecules in a cell.

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What is genomic library?

“A genomic library is a collection of bacteria which have been genetically engineered to hold the entire DNA of an organism”.

A genomic library is a collection of genes or DNA sequences

created using molecular cloning. These libraries are constructed

using clones of bacteria or yeast that contain vectors into which

fragments of partially digested DNA have been inserted. These

bacteria and yeast are subsequently grown in culture and when

these microorganisms replicate their genome, they also replicate

the vector genome contained within them, that is, they replicate

DNA fragments that had been inserted in vectors producing

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clones of the orignal genome. This collection of clones, in

theory, contains all sequences found in the original source,

including the sequence of interest. Genomic libraries can be

constructed using various hosts like plasmids, bacteriophage lambdas , cosmids, YACs and many more.

What are the steps involved in the construction of genomic library?

To create a human genome library, a researcher begins by extracting and purifying DNA from human cell.

The purified DNA consist of extremely long strands.To begin working with DNA, the strands must first be cut into manageable sizes.

The DNA therefore is digested with restriction enzymes which cut the DNA at specific sequences. The restriction

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enzyme cut the DNA into 1000s of smaller fragments, each of which may contain one or more gene.

Each fragment is different and have unique DNA sequence. To create the library,each fragment must be inserted into loops of DNA called plasmids. A plasmid is a type of vector that allows the DNA to be shuttled in bacteria.

The plasmids are digested with the restriction enzymes and then sealed to human DNA using DNA ligase enzyme the resulting molecules are “recombinanat”.

The recombinant DNA molecule are added to bacteria,and the bacteria are made to take up the DNA. When bacteria have taken up the DNA, the entire collection of cells and DNA represents a human genome library. The recombinant plasmids remain separate from the bacteria’s own DNA, making it easy to extract again.

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What is probe? What is it used for in genomic library?

One of the key elements required to identify a gene during

cloning is a probe. “A probe is normally a cloned piece of

DNA that contains a portion of the sequence for which you

are searching”. You typically will make the probe

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radioactive and add it to a solution. Filters containing

immobilized clones are then bathed in the solution. The

principal behind this step is that the probe will bind to any

clone containing sequences similar to those found on the

probe. This binding step is called hybridization. Genomic

DNA libraries are almost always screened by hybridization

using a radioactive nucleic acid probe.

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“Cloning - specific DNA detection by

Hybridization”

1.

2.

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3.

What are the uses of genomic library?

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Using a genomic library, researchers can explore thegenome of an organism to learn moreabout genomic structure and function. They can also mapthe genome, identifying the locations of specific genes.This information becomes extremely useful when researchers want to develop tests which can be used to locate genetic variations including mutations which may be related to congenital conditions. The deeper the understanding of an organism's genome, the more researchers can know about the organism as a whole.

A genomic library can also be used for the purpose of cloning segments of DNA. The vectors in the host bacteria can be replicated by the host to create a number of copies of a segment of interest, with these copies being further studied or inserted into other vectors for genetic modification and other research purposes. Cloned materials, for example, could be inserted into crops for the purpose of introducing specific modifications with the goal of improving crop performance.

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