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(analytical chemistry)
The formation of a faithful mold or replica of a solid that is thin enough for penetration by an electron microscope beam; can use plastic (such as collodion) or vacuum deposition (such as of carbon or metals) to make the mold.
(cell and molecular biology)
Duplication, as of a nucleic acid, by copying from a molecular template.
In experimental design, the repetition of an experiment or parts of an experiment to secure more data as an aid to determining the experimental error and to arrive at better estimates of the effects of various treatments with smaller standard errors.
Multiplication of phage in a bacterial cell.


the collection of data under the same conditions as a previous study. This is often done to test the VALIDITY of the conclusions drawn, since faults in design or analysis may thereby be discovered.



(also reduplication, autoreproduction, and autosynthesis), the process of the self-reproduction, or self-copying, of nucleic acids, genes, and chromosomes that occurs in all living cells. The mechanism of replication is based on the enzymatic synthesis of deoxyribonucleic acid (DNA) or ribo-nucleic acid (RNA), which occurs in accordance with the matrix principle.

The model of the structure of DNA—the double helix—was proposed in 1953 by J. Watson and F. Crick. This model both explained how genetic information is inscribed in a DNA molecule and made it possible to understand and experimentally study the chemical mechanisms of the duplication of genetic material. The strict specificity of the pairing of nitrogen bases in a DNA molecule is responsible for the complementarity of the sequences of bases in two chains and guarantees the precision of replication. The guanine-cytosine pair is stabilized by three hydrogen bonds, and the adenine-thymine pair is stabilized by two hydrogen bonds, thereby sharply diminishing the probability of the incorrect pairing of bases.

According to Watson and Crick, the process of DNA replication provides for the rupture of hydrogen bonds and the unwinding of the strands of a double helix; it also provides for the synthesis of complementary chains on solitary strands. As a result of DNA replication, two similar molecules arise from a single double-chain DNA molecule. In each daughter molecule there is one polynucleotide chain that is parental and one that is resynthesized (the semiconservative mechanism of replication).

DNA replication is a multistage genetically controlled process in which many enzymes participate, including DNA poly-merase, DNA ligase, and DNA methylase. The replication of DNA having a double chain has a fixed beginning and end and an oriented direction. The noncontinuous synthesis of new chains starts where the complementary chains of the parental DNA unwind (Figure 1).

Figure 1. Structure of the Y-fork proposed by the hypothesis of the noncontinuous replication of DNA

At the beginning of each synthesized segment of a DNA chain there is a priming strand of RNA that consists of 50–100 nucleotides. The fragments of the DNA chains, each containing about 1,000 nucleotides, gradually form on the RNA with the participation of DNA polymerase. The primer RNA is then destroyed by ribonuclease, while the synthesized DNA fragments are combined to form long chains by the enzyme polynu-cleotideligase.

Replication is unique in viruses and bacteriophages that have DNA composed of a single strand. DNA composed of a single chain [the (+)-chain] is introduced into the host cell, after which a complementary chain [the (–)-chain] is synthesized on the (+)-chain serving as a matrix. New single-chain (+)-chains, which form new viral particles, are synthesized on the double-helix molecule that has formed (the replicative form). Viruses and bacteriophages that contain RNA replicate by the same principle. Therefore, in all known cases of replication, DNA and RNA pass through a stage during which molecules have a double chain.

Eucaryotes are higher organisms whose cells contain a formed nucleus. The main genetic function in eucaryotes is performed by complex structures known as chromosomes, which consist of DNA, RNA, proteins, and other substances. The replication of DNA and other chromosomal components occurs during interphase, which precedes cell division. The doubled chromosomes subsequently disjoin and become evenly distributed between daughter cells. Thus, all hereditary information is transmitted relatively unchanged from cell to cell from one generation to the next.


Watson, J. Molekuliarnaia biologiia gena. Moscow, 1967. (Translated from English.)
Ratner, V. A. Printsipy organizatsii i mekhanizmy molekuliarno-geneticheskikh protsessov. Novosibirsk, 1972.
Bresler, S. E. Molekuliarnaia biologiia. Leningrad, 1973.
Stent, G. Molekuliarnaia genetika. Moscow, 1974. (Translated from English.)



(database, networking)
Creating and maintaining a duplicate copy of a database or file system on a different computer, typically a server. The term usually implies the intelligent copying of parts of the source database which have changed since the last replication with the destination.

Replication may be one-way or two-way. Two-way replication is much more complicated because of the possibility that a replicated object may have been updated differently in the two locations in which case some method is needed to reconcile the different versions.

For example, Lotus Notes can automatically distribute document databases across telecommunications networks. Notes supports a wide range of network protocols including X25 and Internet TCP/IP.

Compare mirror. See also rdist.


In database management, the ability to keep distributed databases synchronized by routinely copying the entire database or subsets of the database to other servers in the network.

There are various replication methods. Primary site replication maintains the master copy of the data in one site and sends read-only copies to the other sites. In a workflow environment, the master copy can move from one site to another. This is called "shared replication" or "transferred ownership replication." In symmetric replication, also called "update-anywhere" or "peer-to-peer replication," each site can receive updates, and all other sites are then updated. Failover replication, or hot backup, maintains an up-to-date copy of the data at a different site for backup. See mirroring, disaster recovery and distributed database.
References in periodicals archive ?
In addition to system redundancy, real-time (synchronous) data mirroring to independent storage systems provides a highly persistent and fault tolerant data environment.
For example, when data is created by one of the core business financial applications it might be held on a primary storage system that is very responsive with sophisticated data mirroring and rolling-backup systems in place to ensure that the information may be retrieved rapidly and is robustly protected.
The Appro AR3015 NAS, 3U high-density profile storage system features up to 6 terabytes of easy-to-manage storage capacity with 15 SATA hot-swap hard disk bays, giving network administrators enterprise-level features such as data mirroring and fail-over, snapshot data recovery and UPS support for mission critical applications.
These sit alongside continuity applications that include data mirroring packages and storage management tools.
The appliances include complete data management capabilities including iRep replication to facilitate data mirroring, snapshot technology and tape backup.
This platform allows user-defined policies to define content filtering, traffic prioritizing (QoS), rate limiting, monitoring, and data mirroring capabilities for network traffic.
Akara's technology will allow Ciena to offer high performance long-distance data mirroring and disaster recovery systems at a lower cost, opening the market to medium-sized businesses.
There's an aspect of data mirroring to this--but it's not simply a data mirror," said StorageTek's senior product marketing manager Bill Chait.
Perhaps the most concise clarification is provided in "Mirroring Isn't Backup" by Rick Cook: Although data mirroring, especially remote mirroring, is an important tool in business continuity and disaster recovery, it is not a substitute for conventional backups.
The Raid-1 option implements data mirroring between the two 10,000-rpm SCSI drives, thereby providing redundancy by duplicating all data from one drive onto the other drive.
INRANGE's distance extension or "virtual storage networking" technologies for storage infrastructures include top-performing channel extension systems that are used to enable industry-leading data mirroring applications from EMC, IBM, and Hitachi Data Systems.