What is a plasmid?
Q: What is a plasmid?
A: A plasmid is a DNA molecule that is separate from the chromosomal DNA and can replicate independently. It is double stranded and, in many cases, circular in shape.
Q: Who introduced the term "plasmid"?
A: The term "plasmid" was first introduced by American molecular biologist Joshua Lederberg in 1952.
Q: How big are plasmids?
A: Plasmids vary in size from 1 to over 1,000 kilobase pairs (kbp).
Q: Where do plasmids occur naturally?
A: Plasmids usually occur naturally in bacteria but are sometimes found in eukaryotic organisms such as Saccharomyces cerevisiae.
Q: What does horizontal gene transfer have to do with plasmids?
A: Plasmids are often associated with conjugation, a mechanism of horizontal gene transfer.
Q: Are plasmids considered alive?
A: No, similar to viruses, plasmids are not considered a form of life as it is currently defined.
Q: What advantages may be conferred by carrying certain genes on a plasmid?
A: Carrying certain genes on a plasmid may provide bacteria with an ability to fix elemental nitrogen or degrade difficult organic compounds which could provide an advantage under conditions of nutrient deprivation.
