Replicon (genetics)
Encyclopedia
A replicon is a DNA
molecule or RNA
molecule, or a region of DNA or RNA, that replicates
from a single origin of replication
.
For most prokaryotic chromosomes, the replicon is the entire chromosome. One notable exception found comes from archaea
, where two Sulfolobus
species have been shown to contain three replicons. Examples of bacterial species that have been found to possess multiple replicons include: Rhodobacter sphaeroides
(2), Vibrio cholerae
, and Burkholderia multivorans
(3). These "secondary" (or tertiary) chromosomes are often described as a molecule that is a mixture between a true chromosome
and a plasmid
and are sometimes called "chromids".
Plasmid
s and bacteriophage
s are usually replicated as single replicons, but large plasmids in Gram-negative bacteria have been shown to carry several replicons.
For eukaryotic chromosomes, there are multiple replicons per chromosome. The definition of replicons is somewhat confused with mitochondria
, as they use unidirectional replication with two separate origins.
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
molecule or RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
molecule, or a region of DNA or RNA, that replicates
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
from a single origin of replication
Origin of replication
The origin of replication is a particular sequence in a genome at which replication is initiated. This can either be DNA replication in living organisms such as prokaryotes and eukaryotes, or RNA replication in RNA viruses, such as double-stranded RNA viruses...
.
For most prokaryotic chromosomes, the replicon is the entire chromosome. One notable exception found comes from archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...
, where two Sulfolobus
Sulfolobus
Sulfolobus is a genus of microorganism in the family Sulfolobaceae. It belongs to the archea domain.Sulfolobus species grow in volcanic springs with optimal growth occurring at pH 2-3 and temperatures of 75-80 °C, making them acidophiles and thermophiles respectively...
species have been shown to contain three replicons. Examples of bacterial species that have been found to possess multiple replicons include: Rhodobacter sphaeroides
Rhodobacter sphaeroides
Rhodobacter sphaeroides is a kind of purple bacteria; a group of bacteria that can obtain energy through photosynthesis. Its best growth conditions are anaerobic phototrophy and aerobic chemoheterotrophy in the absence of light. R. sphaeroides is also able to fix nitrogen...
(2), Vibrio cholerae
Vibrio cholerae
Vibrio cholerae is a Gram-negative, comma-shaped bacterium. Some strains of V. cholerae cause the disease cholera. V. cholerae is facultatively anaerobic and has a flagella at one cell pole. V...
, and Burkholderia multivorans
Burkholderia multivorans
Burkholderia multivorans is a species in Phylum proteobacteria. It is known to cause human disease, such as colonisation of the lung in cystic fibrosis....
(3). These "secondary" (or tertiary) chromosomes are often described as a molecule that is a mixture between a true chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
and a plasmid
Plasmid
In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...
and are sometimes called "chromids".
Plasmid
Plasmid
In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...
s and bacteriophage
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
s are usually replicated as single replicons, but large plasmids in Gram-negative bacteria have been shown to carry several replicons.
For eukaryotic chromosomes, there are multiple replicons per chromosome. The definition of replicons is somewhat confused with mitochondria
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
, as they use unidirectional replication with two separate origins.