BRAINCAKEPlasmids
A plasmid is a small, circular loop of double-stranded DNA found in the cytoplasm of many bacteria, separate from the main bacterial chromosome in the nucleoid. Plasmids are much smaller than the chromosome, usually a few thousand base pairs long, and a single cell may contain one copy or many copies of the same plasmid. Not every bacterium has plasmids.
Plasmids replicate independently of the bacterial chromosome, using their own origin of replication. This means a cell can build up several copies, and copies are passed to both daughter cells when the bacterium divides by binary fission.
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Key terms in this lesson
- horizontal gene transfer
- The transfer of genetic material between organisms other than from parent to offspring, for example plasmid transfer between bacteria.
More in Prokaryotic Cells
- Bacterial Cell
- Pili and Flagella
- Cell Surface Membrane
- Nucleoid
- 70S Ribosomes
- Gram-Staining
- Antibiotics
- Alternative Classification of Bacteria
All 31 lessons in Prokaryotic Cells · All Edexcel AS-level Biology topics