A concatemer is a long continuous

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

molecule that contains multiple copies of the same DNA sequence linked in series. These

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

ic molecules are usually copies of an entire

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

linked end to end and separated by ''cos'' sites (a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

binding

nucleotide sequence A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nu ...

that occurs once in each copy of the genome). Concatemers are frequently the result of

rolling circle replication Rolling circle replication (RCR) is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genom ...

, and may be seen in the late stage of infection of bacteria by

phage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, and may have structures tha ...

s. As an example, if the genes in the phage DNA are arranged ABC, then in a concatemer the genes would be ABCABCABCABC and so on (assuming synthesis was initiated between genes C and A). They are further broken by

ribozyme Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to Catalysis, catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozy ...

s. During active infection, some species of viruses have been shown to replicate their genetic material via the formation of concatemers. In the case of ''

human herpesvirus-6 Human herpesvirus 6 (HHV-6) is the common collective name for human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B). These closely related viruses are two of the nine known herpesviruses that have humans as their primary host. HHV-6 ...

'', its entire genome is made over and over on a single strand. These long concatemers are subsequently cleaved between the pac-1 and pac-2 regions by

ribozymes Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozymes demons ...

when the genome is packaged into individual virions.

Bacteriophage T4 Escherichia virus T4 is a species of bacteriophages that infect ''Escherichia coli'' bacteria. It is a double-stranded DNA virus in the subfamily '' Tevenvirinae'' of the family '' Straboviridae''. T4 is capable of undergoing only a lytic li ...

replicating DNA was labeled with tritiated

thymidine Thymidine (nucleoside#List of nucleosides and corresponding nucleobases, symbol dT or dThd), also known as deoxythymidine, deoxyribosylthymine, or thymine deoxyriboside, is a pyrimidine nucleoside, deoxynucleoside. Deoxythymidine is the DNA nuc ...

and examined by

autoradiograph An autoradiograph is an image on an X-ray film or nuclear emulsion produced by the pattern of decay emissions (e.g., beta particles or gamma rays) from a distribution of a radioactive substance. Alternatively, the autoradiograph is also availab ...

y. The observed

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all life, living organisms, acting as the most essential part of heredity, biolog ...

intermediates included circular and branched circular concatemeric structures that likely arose by

. When assembling concatemers from synthetic oligonucleotides, increasing salt concentration to 200 mM was found to be a major optimizing factor due to its ability to enhance ionic strength, which hastened the formation of concatemers.

References

Bibliography

* Oxford Dictionary of Biochemistry and Molecular Biology, 2nd ed. R. l., eds. Oxford University Press, 2006. p. 138. Repetitive DNA sequences {{genetics-stub