A plasmid is a very short ring of DNA, which can carry several different genes. A gene is a sequence of DNA that has the genetic code, or blueprint, to create a protein (or several proteins). These proteins then can carry out a multitude of tasks, such building bones or catalyzing (help carry out) reactions. Plasmids are really cool for a couple of reasons: one, they can be shared between bacteria. Two, because plasmids can be shared, or given to bacteria, plasmids can be genetically engineered in a laboratory to carry out a specific experiment, and then put inside bacteria. Bacteria will grow the plasmid as their own DNA, effectively copying the designed plasmid.
This is what a plasmid might look like:
Quite often there is also a gene on the plasmid that offers resistance to an antibiotic, typically ampicillin. This allows one to select bacteria that have the plasmids from ones that don't by growing them on what is called selective media. If the gene gives bacteria resistance to ampillicin, the bacteria will then be grown on a medium with ampicillin, so that any bacteria that do not have the plasmid (and therefore the gene for resistance) will not survive.
After a plasmid has been constructed (which has been the topic of my project thus far), it can be transformed into bacteria for duplication. Unless the plasmid hurts the bacteria, the bacteria will grow millions of copies of the plasmid.
