Plasmids

Plasmid

a small, circular, double stranded DNA molecule, which can replicate independently from its chromosomal DNA. If plasmids are used for experiments, they are called vectors.

because genes in plasmids often provide the bacteria with genetic advantages, including for example antibiotic resistance. Scientists use plasmids as tools for cloning, transferring and manipulating genes.

Why are they important

Plasmids are most commonly found in the cytoplasm of bacterium or protozoan, but they can also occurs in certain eukaryotic cells.

Where are they found

DNA genes into the plasmid vectors, which results in a recombinant plasmid. Using the process "transformation", those plasmids can then be put into another bacteria and because bacterias divide often, those DNA fragments can be copied quickly in great amounts.

How are they inserted

How are they transmitted

Before transformation, bacteria are treated with a chemical called calcium chloride, which causes water to enter into the cells and makes them swell. These swollen bacteria are then known as competent bacteria.

Next, plasmid DNA (containing the foreign DNA) is mixed with the competent bacteria and the solution is heated. The plasmid DNA enter the bacteria through small pores created in the cell membranes. Once in the host cell, the plasmid DNA is copied many times by the bacteria's own DNA replicating machinery.