Circular DNA molecules found in bacteriaReplicated by the host’s machinery independently of the genome. This is accomplished by a sequence on the plasmid called ori, for origin of replication.
In order to study a DNA fragment (e.g., a gene), it needs to be amplified and eventually purified. In order to study a DNA fragment (e.g., a gene), it needs to be amplified and eventually purified.Accomplished by cloning the DNA into a vector. This vector is a plasmid is small, circular DNA molecule that replicates inside a bacterium such as Escherichia coli.
Plasmids also contain selectable markers. Plasmids also contain selectable markers. Genes encoding proteins which provide a selection for rapidly and easily finding bacteria containing the plasmid. Provide resistance to an antibiotic (ampicillin, kanamycin, tetracycline, chloramphenicol, etc.). Thus, bacteria will grow on medium containing these antibiotics only if the bacteria contain a plasmid with the appropriate selectable marker.
DNA library - a random collection of DNA fragments from an organism cloned into a vector DNA library - a random collection of DNA fragments from an organism cloned into a vector Ideally contains at least one copy of every DNA sequence. Easily maintained in the laboratoryCan be manipulated in various ways to facilitate the isolation of a DNA fragment of interest to a scientist. Numerous types of libraries exist for various organisms - Genomic and cDNA.
Gentle lysis step to break open the cells and release the plasmid DNA into solution. Gentle lysis step to break open the cells and release the plasmid DNA into solution. Cell debris and chromosomal DNA of the bacteria is pelleted during the centrifugation. Plasmid DNA remains behind in the clear nonpelleted fraction (the nonpelleted solution left after centrifugation is known as the supernatant).Subsequent steps are then performed on the supernatant to remove contaminating RNA and proteins from the plasmid DNA.
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