plasmid

plas·mid

(plăz'mĭd) pronunciation

n.
A circular, double-stranded unit of DNA that replicates within a cell independently of the chromosomal DNA. Plasmids are most often found in bacteria and are used in recombinant DNA research to transfer genes between cells.

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Genetic element not contained within a chromosome. It occurs in many bacterial strains. Plasmids are circular DNA molecules that replicate independently of the bacterial chromosome. They are not essential for the bacterium but may give it a selective advantage. Some plasmids determine the production of proteins that can kill other bacteria; others make bacteria resistant to antibiotics. Plasmids are extremely valuable tools in the fields of molecular biology and genetics, specifically in the area of genetic engineering.

For more information on plasmid, visit Britannica.com.

McGraw-Hill Science & Technology Encyclopedia:

Plasmid

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A circular extrachromosomal genetic element that is ubiquitous in prokaryotes and has also been identified in a number of eukaryotes. In general, bacterial plasmids can be classified into two groups on the basis of the number of genes and functions they carry. The larger plasmids are deoxyribonucleic acid (DNA) molecules of around 100 kilobase (kb) pairs, which is sufficient to code for approximately 100 genes. There is usually a small number of copies of these plasmids per host chromosome, so that their replication must be precisely coordinated with the cell division cycle. The plasmids in the second group are smaller in size, about 6–10 kb. These plasmids may harbor 6–10 genes and are usually present in multiple copies (10–20 per chromosome). See also Gene.

Plasmids have been identified in a large number of bacterial genera. Some bacterial species harbor plasmids with no known functions (cryptic plasmids) which have been identified as small circular molecules present in the bacterial DNA. The host range of a particular plasmid is usually limited to closely related genera. Some plasmids, however, are much more promiscuous and have a much broader host range.

The functions specified by different bacterial plasmids are usually quite specialized in nature. Moreover, they are not essential for cell growth since the host bacteria are viable without a plasmid when the cells are cultured under conditions that do not select for plasmid-specified gene products. Plasmids thus introduce specialized functions to host cells which provide versatility and adaptability for growth and survival. Plasmids which confer antibiotic resistance (R plasmids) have been extensively characterized because of their medical importance. Plasmids have played a seminal role in the spectacular advances in the area of genetic engineering. Individual genes can be inserted into specific sites on plasmids in cell cultures and the recombinant plasmid thus formed introduced into a living cell by the process of bacterial transformation. See also Genetic engineering.

Gale Genetics Encyclopedia:

Plasmid

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Plasmids are naturally occurring, stable genetic elements found in bacteria, fungi, and even in the mitochondria of some plants. They may be composed of DNA or RNA, double-stranded or single-stranded, linear or circular. Plasmids almost always exist and replicate independently of the chromosome of the cell in which they are found.

Types of Plasmids

Plasmids are not usually required by their host cell for its survival. Instead, they carry genes that confer a selective advantage on their host, such as resistance to heavy metals or resistance to naturally made antibiotics carried by other organisms. Alternatively, they may produce antibiotics (toxins) that help the host to compete for food or space. For instance, antibiotic resistance genes produced by a plasmid will allow its host bacteria to grow even in the presence of competing bacteria or fungi that produce these antibiotics.

Plasmids are subgrouped into five main types based on phenotypic function. R plasmids carry genes encoding resistance to antibiotics. Col plasmids confer on their host the ability to produce antibacterial polypeptides called bacteriocins that are often lethal to closely related or other bacteria. The col proteins of E. coli are encoded by plasmids such as ColE1. F plasmids contain the F or fertility system required for conjugation (the transfer of genetic information between two cells). These are also known as episomes because, under some circumstances, they can integrate into the host chromosome and thereby promote the transfer of chromosomal DNA between bacterial cells. Degradative or catabolic plasmids allow a host bacterium to metabolize normally undegradable or difficult compounds such as various pesticides. Finally, virulence plasmids confer pathogenicity on a host organism by the production of toxins or other virulence factors.

Replication

One common feature of all plasmids is a specific sequence of nucleotides termed an origin of replication (ori). This sequence, together with other regulatory sequences, is referred to as a replicon. The replicon allows a plasmid to replicate within a host cell independently of the host cell's own replication cycle. If the plasmid makes many copies of itself per cell, it is termed a "relaxed" plasmid. If it maintains itself in fewer numbers within the cell it is termed a "stringent" plasmid. Two different plasmids can coexist in the same cell only if they share the same replication elements. If they do not, they will be unable to be propagated stably in the same cell line, and are termed incompatible.

In nature, plasmid inheritance can occur through a variety of mechanisms. During conjugation between two bacterial strains, plasmids can be transferred along with the bacterial DNA, and this activity is controlled by a set of transfer (tra) genes that are located on the plasmid and not on the bacterial chromosome. The proteins produced by these transfer genes bind to the DNA at the ori site to form a DNA-protein complex known as a relaxosome. This complex makes a nick, or break, in one of the two strands of the double-stranded plasmid DNA molecule. The place where this break occurs is called the "nic" site, and the nicked DNA is said to be "relaxed" because the DNA unwinds as a result of the nick in one of the strands. The single-stranded DNA that is generated by the nick is thought to be unwound and transferred through the pilus, or mating bridge, that connects the two bacteria entering the recipient bacteria. The other strand is left in the donor bacteria. It acts as a template for the synthesis of a new complementary DNA strand forming a double-stranded plasmid DNA molecule.

Some nonconjugative plasmids can also be transferred into bacteria by means of a process called mobilization, as long as they carry the necessary (mob) genes. Others are taken up by bacterial cells during the process known as transformation. Finally, plasmids that exist in a host cell that undergoes fission (cell division) are simply divided between the resultant two daughter cells.

Use in Research and Technology

Because of their ability to move genes from cell to cell, plasmids have become versatile tools for both research and biotechnology. In the laboratory, researchers use plasmids to carry marker genes, allowing them to trace the plasmid's inheritance across host cells. Transferred or "cloned" genes are used to produce a variety of important medical, agricultural, or environmental products that can be economically used by humans.

Researchers have also engineered plasmids to be extremely efficient cloning vectors. To be used in this way, the plasmid must contain at least one origin of replication, a multiple cloning site (called a polylinker) where a variety of restriction enzymes can cut so that foreign DNA can be inserted, a selectable genetic marker, and transcription and translation signals recognized by the host cell, so that the expression of a cloned gene can be easily identified.

The foreign DNA is often inserted in such a way that the expression of the foreign gene is tied to the expression of a marker gene. For example, one of the most popular methods to show that a foreign DNA has been inserted and expressed in the host is by the insertional inactivation of the lac Z gene. In this case, the foreign DNA is inserted in the middle of the lac Z gene so that the gene becomes defective and the enzyme it codes for no longer works. The damaged enzyme therefore cannot cleave the artificial substrate Xgal to produce a blue color or blue colony, as it normally would, and white colonies of bacteria are produced. Therefore, the white colonies indicate that artificial DNA has been successfully cloned or recombined into the plasmid in the lac Z gene, whereas nonrecombinant colonies are blue. The white colonies can thus be easily isolated for further expansion and experimentation.

Under certain circumstances, recombinant DNA experiments using plasmids are considered to be hazardous, and the ease with which plasmids are acquired by bacteria has led them to be classed as biohazards. They are therefore subject to guidelines and may require registration and approval. A publication produced by the National Institutes of Health, titled Guidelines for Research Involving Recombinant DNA Molecules, is the definitive reference for recombinant DNA research in the United States and should be consulted when considering research, particularly biomedical research, involving plasmids.

Bibliography

Alberts, Bruce, et al. Molecular Biology of the Cell, 4th ed. New York: Garland Science,2002.

Bloom, Mark V., Greg A. Freyer, and David A. Micklos. Laboratory DNA Science: An Introduction to Recombinant DNA Techniques and Methods of Genome Analysis. Menlo Park, CA: Addison-Wesley, 1996.

Alcamo, I. Edward. DNA Technology: The Awesome Skill, 2nd ed. Burlington, MA: Harcourt Press, 2000.

Lodish, Harvey, et al. Molecular Cell Biology, 4th ed. New York: W. H. Freeman,1999.

—Linnea Fletcher

Dictionary of Cultural Literacy: Science:

plasmid

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A circular bacterial DNA, sometimes used as a vector for gene insertion or genetic engineering. Plasmids are often the site of genes that code for resistance to antibiotics.

Oxford Dictionary of Biochemistry:

plasmid

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strictly any extrachromosomal genetic element; however, mitochondrial and chloroplast DNA, yeast killer, and other cases are commonly excluded, hence the term plasmid generally refers to an extrachromosomal covalently continuous double-stranded DNA molecule that occurs in bacteria and (rarely) other microorganisms. Natural plasmids vary from <5 kb to over 100 kb in size. They are classified in a number of different ways: the copy number describes the ratio of plasmid/chromosome molecules, and is greatly influenced by the nature of the origin of replication. Plasmids under stringent control have a copy number of one and those under relaxed control may have copy numbers of hundreds per cell. The host range describes the variety of species that can act as host (see also incompatibility). Plasmids capable of transfer are said to be conjugal; wide host-range, conjugal plasmids are described as promiscuous. Plasmid genes include drug resistance (resistance plasmids), genes for catabolic enzymes (catabolic plasmids), genes for antibiotic synthesis, and genes for toxin production. Plasmids are popular choices for cloning vectors. and is greatly influenced by the nature of the origin of replication. Plasmids under stringent control have a copy number of one and those under relaxed control may have copy numbers of hundreds per cell. The host range describes the variety of species that can act as host (see also incompatibility). Plasmids capable of transfer are said to be conjugal; wide-host-range conjugal plasmids are described as promiscuous. Plasmid genes include drug resistance (resistance plasmids), genes for catabolic enzymes (catabolic plasmids), genes for antibiotic synthesis, and genes for toxin production. Plasmids are popular choices for cloning vectors.

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Saunders Veterinary Dictionary:

plasmid

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An extrachromosomal self-replicating genetic element of a cell. In bacteria, plasmids are circular DNA molecules that reproduce themselves and are thus conserved, apart from the chromosome, through successive cell divisions; they include the F factor and R factor.

R factor p. — see R factor.
relaxed p. — occurs in tens to several hundred copies per bacterium and are dependent solely on host enzymes for replication.

Mosby's Dental Dictionary:

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Any type of intracellular inclusion considered to have a genetic function.

Random House Word Menu:

categories related to 'plasmid'

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Random House Word Menu by Stephen Glazier

For a list of words related to plasmid, see:

Genetics, Heredity, and Evolution - plasmid: small DNA molecule outside chromosome in prokaryotic organism that reproduces independently

Wikipedia on Answers.com:

Plasmid

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For the physics phenomena, see plasmoid.

For the computer user interface, see KDE Plasma Workspaces.

Figure 1: Illustration of a bacterium with plasmid enclosed showing genomic DNA and plasmids.

In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA.^[1] They are double-stranded and, in many cases, circular. Plasmids usually occur naturally in bacteria, but are sometimes found in eukaryotic organisms (e.g., the 2-micrometre ring in Saccharomyces cerevisiae).

Plasmid sizes vary from 1 to over 1,000 kbp. The number of identical plasmids in a single cell can range anywhere from one to even thousands under some circumstances. Plasmids can be considered part of the mobilome because they are often associated with conjugation, a mechanism of horizontal gene transfer.

The term plasmid was first introduced by the American molecular biologist Joshua Lederberg in 1952.^[2]

Plasmids are considered replicons, capable of replicating autonomously within a suitable host. Plasmids can be found in all three major domains: Archaea, Bacteria, and Eukarya.^[1] Similar to viruses, plasmids are not considered by some to be a form of life.^[3] Unlike viruses, plasmids are naked DNA and do not encode genes necessary to encase the genetic material for transfer to a new host, though some classes of plasmids encode the sex pilus necessary for their own transfer. Plasmid host-to-host transfer requires direct, mechanical transfer by conjugation or changes in host gene expression allowing the intentional uptake of the genetic element by transformation.^[1] Microbial transformation with plasmid DNA is neither parasitic nor symbiotic in nature, because each implies the presence of an independent species living in a commensal or detrimental state with the host organism. Rather, plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state. Plasmids may carry genes that provide resistance to naturally occurring antibiotics in a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances. Plasmids can also provide bacteria with the ability to fix elemental nitrogen or to degrade recalcitrant organic compounds that provide an advantage when nutrients are scarce.^[1]

Contents

1 Vectors
2 Applications
- 2.1 Disease models
- 2.2 Gene therapy
3 Episomes
4 Types
5 Yeast plasmids
6 Plasmid DNA extraction
7 Conformations
8 Simulation of plasmids
9 See also
10 References
11 Further reading
- 11.1 Episomes
12 External links

Vectors

There are two types of plasmid integration into a host bacteria: Non-integrating plasmids replicate as with the top instance, whereas episomes, the lower example, integrate into the host chromosome.

Further information: Vector (molecular biology)

Plasmids used in genetic engineering are called vectors. Plasmids serve as important tools in genetics and biotechnology labs, where they are commonly used to multiply (make many copies of) or express particular genes.^[4] Many plasmids are commercially available for such uses. The gene to be replicated is inserted into copies of a plasmid containing genes that make cells resistant to particular antibiotics and a multiple cloning site (MCS, or polylinker), which is a short region containing several commonly used restriction sites allowing the easy insertion of DNA fragments at this location. Next, the plasmids are inserted into bacteria by a process called transformation. Then, the bacteria are exposed to the particular antibiotics. Only bacteria that take up copies of the plasmid survive, since the plasmid makes them resistant. In particular, the protecting genes are expressed (used to make a protein) and the expressed protein breaks down the antibiotics. In this way, the antibiotics act as a filter to select only the modified bacteria. Now these bacteria can be grown in large amounts, harvested, and lysed (often using the alkaline lysis method) to isolate the plasmid of interest.

Another major use of plasmids is to make large amounts of proteins. In this case, researchers grow bacteria containing a plasmid harboring the gene of interest. Just as the bacterium produces proteins to confer its antibiotic resistance, it can also be induced to produce large amounts of proteins from the inserted gene. This is a cheap and easy way of mass-producing a gene or the protein it then codes for, for example, insulin or even antibiotics.

However, a plasmid can contain inserts of only about 1–10 kbp. To clone longer lengths of DNA, lambda phage with lysogeny genes deleted, cosmids, bacterial artificial chromosomes, or yeast artificial chromosomes are used.

Applications

Disease models

Plasmids were historically used to genetically engineer the embryonic stem cells of rats in order to create rat genetic disease models. The limited efficiency of plasmid-based techniques precluded their use in the creation of more accurate human cell models. However, developments in Adeno-associated virus recombination techniques, and Zinc finger nucleases, have enabled the creation of a new generation of isogenic human disease models.

Gene therapy

The success of some strategies of gene therapy depends on the efficient insertion of therapeutic genes at the appropriate chromosomal target sites within the human genome, without causing cell injury, oncogenic mutations (cancer) or an immune response. Plasmid vectors are one of many approaches that could be used for this purpose. Zinc finger nucleases (ZFNs) offer a way to cause a site-specific double-strand break to the DNA genome and cause homologous recombination. This makes targeted gene correction a possibility in human cells. Plasmids encoding ZFN could be used to deliver a therapeutic gene to a pre-selected chromosomal site with a frequency higher than that of random integration. Although the practicality of this approach to gene therapy has yet to be proven, some aspects of it could be less problematic than the alternative viral-based delivery of therapeutic genes.^[5]

Episomes

Episomes are the eukaryotic equivalent of bacterial plasmids. In general, in eukaryotes, episomes are closed circular DNA molecules that are replicated in the nucleus. Viruses are the most common examples of this, such as herpesviruses, adenoviruses, and polyomaviruses. Other examples include aberrant chromosomal fragments, such as double minute chromosomes, that can arise during artificial gene amplifications or in pathologic processes (e.g., cancer cell transformation). Episomes in eukaryotes behave similarly to plasmids in prokaryotes in that the DNA is stably maintained and replicated with the host cell. Cytoplasmic viral episomes (as in poxvirus infections) can also occur. Some episomes, such as herpesviruses, replicate in a rolling circle mechanism, similar to bacterial phage viruses. Others replicate through a bidirectional replication mechanism (Theta type plasmids). In either case, episomes remain physically separate from host cell chromosomes. Several cancer viruses, including Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus, are maintained as latent, chromosomally-distinct episomes in cancer cells, where the viruses express oncogenes that promote cancer cell proliferation. In cancers, these episomes passively replicate together with host chromosomes when the cell divides. When these viral episomes initiate lytic replication to generate multiple virus particles, they in general activate cellular innate immunity defense mechanisms that kill the host cell.

Types

Overview of bacterial conjugation

Electron micrograph of a DNA fiber bundle, presumably of a single bacterial chromosome loop.

Electron micrograph of a bacterial DNA plasmid (chromosome fragment).

One way of grouping plasmids is by their ability to transfer to other bacteria. Conjugative plasmids contain tra genes, which perform the complex process of conjugation, the transfer of plasmids to another bacterium (Fig. 4). Non-conjugative plasmids are incapable of initiating conjugation, hence they can be transferred only with the assistance of conjugative plasmids. An intermediate class of plasmids are mobilizable, and carry only a subset of the genes required for transfer. They can parasitize a conjugative plasmid, transferring at high frequency only in its presence. Plasmids are now being used to manipulate DNA and may possibly be a tool for curing many diseases.

It is possible for plasmids of different types to coexist in a single cell. Several different plasmids have been found in E. coli. However, related plasmids are often incompatible, in the sense that only one of them survives in the cell line, due to the regulation of vital plasmid functions. Thus, plasmids can be assigned into compatibility groups.

Another way to classify plasmids is by function. There are five main classes:

Fertility F-plasmids, which contain tra genes. They are capable of conjugation.
Resistance (R)plasmids, which contain genes that can build a resistance against antibiotics or poisons and help bacteria produce pili. Historically known as R-factors, before the nature of plasmids was understood.
Col plasmids, which contain genes that code for bacteriocins, proteins that can kill other bacteria.
Degradative plasmids, which enable the digestion of unusual substances, e.g. toluene and salicylic acid.
Virulence plasmids, which turn the bacterium into a pathogen.

Plasmids can belong to more than one of these functional groups.

Plasmids that exist only as one or a few copies in each bacterium are, upon cell division, in danger of being lost in one of the segregating bacteria. Such single-copy plasmids have systems that attempt to actively distribute a copy to both daughter cells. These systems are often referred to as the partition system or partition function of a plasmid.

Some plasmids or microbial hosts include an addiction system or postsegregational killing system (PSK), such as the hok/sok (host killing/suppressor of killing) system of plasmid R1 in Escherichia coli.^[6] This variant produces both a long-lived poison and a short-lived antidote. Several types of plasmid addiction systems (toxin/ antitoxin, metabolism-based, ORT systems) were described in the literature^[7] and used in biotechnical (fermentation) or biomedical (vaccine therapy) applications. Daughter cells that retain a copy of the plasmid survive, while a daughter cell that fails to inherit the plasmid dies or suffers a reduced growth-rate because of the lingering poison from the parent cell. Finally, the overall productivity could be enhanced.

Yeast plasmids

Other types of plasmids are often related to yeast cloning vectors that include:

Yeast integrative plasmid (YIp), yeast vectors that rely on integration into the host chromosome for survival and replication, and are usually used when studying the functionality of a solo gene or when the gene is toxic. Also connected with the gene URA3, that codes an enzyme related to the biosynthesis of pyrimidine nucleotides (T, C);
Yeast Replicative Plasmid (YRp), which transport a sequence of chromosomal DNA that includes an origin of replication. These plasmids are less stable, as they can get lost during the budding.

Plasmid DNA extraction

As alluded to above, plasmids are often used to purify a specific sequence, since they can easily be purified away from the rest of the genome. For their use as vectors, and for molecular cloning, plasmids often need to be isolated.

There are several methods to isolate plasmid DNA from bacteria, the archetypes of which are the miniprep and the maxiprep/bulkprep.^[4] The former can be used to quickly find out whether the plasmid is correct in any of several bacterial clones. The yield is a small amount of impure plasmid DNA, which is sufficient for analysis by restriction digest and for some cloning techniques.

In the latter, much larger volumes of bacterial suspension are grown from which a maxi-prep can be performed. In essence, this is a scaled-up miniprep followed by additional purification. This results in relatively large amounts (several micrograms) of very pure plasmid DNA.

In recent times, many commercial kits have been created to perform plasmid extraction at various scales, purity, and levels of automation. Commercial services can prepare plasmid DNA at quoted prices below $300/mg in milligram quantities and $15/mg in gram quantities (early 2007^[update]).

Conformations

Plasmid DNA may appear in one of five conformations, which (for a given size) run at different speeds in a gel during electrophoresis. The conformations are listed below in order of electrophoretic mobility (speed for a given applied voltage) from slowest to fastest:

Nicked open-circular DNA has one strand cut.
Relaxed circular DNA is fully intact with both strands uncut, but has been enzymatically relaxed (supercoils removed). This can be modeled by letting a twisted extension cord unwind and relax and then plugging it into itself.
Linear DNA has free ends, either because both strands have been cut or because the DNA was linear in vivo. This can be modeled with an electrical extension cord that is not plugged into itself.
Supercoiled (or covalently closed-circular) DNA is fully intact with both strands uncut, and with an integral twist, resulting in a compact form. This can be modeled by twisting an extension cord and then plugging it into itself.
Supercoiled denatured DNA is like supercoiled DNA, but has unpaired regions that make it slightly less compact; this can result from excessive alkalinity during plasmid preparation.

The rate of migration for small linear fragments is directly proportional to the voltage applied at low voltages. At higher voltages, larger fragments migrate at continuously increasing yet different rates. Thus, the resolution of a gel decreases with increased voltage.

At a specified, low voltage, the migration rate of small linear DNA fragments is a function of their length. Large linear fragments (over 20 kb or so) migrate at a certain fixed rate regardless of length. This is because the molecules 'resperate', with the bulk of the molecule following the leading end through the gel matrix. Restriction digests are frequently used to analyse purified plasmids. These enzymes specifically break the DNA at certain short sequences. The resulting linear fragments form 'bands' after gel electrophoresis. It is possible to purify certain fragments by cutting the bands out of the gel and dissolving the gel to release the DNA fragments.

Because of its tight conformation, supercoiled DNA migrates faster through a gel than linear or open-circular DNA.

Simulation of plasmids

The use of plasmids as a technique in molecular biology is supported by bioinformatics software. These programmes record the DNA sequence of plasmid vectors, help to predict cut sites of restriction enzymes, and to plan manipulations. Examples of software packages that handle plasmid maps are pDraw32, Geneious, Lasergene, GeneConstructionKit, ApE, Clone Manager, and Vector NTI.

References

^ ^a ^b ^c ^d Lipps G (editor). (2008). Plasmids: Current Research and Future Trends. Caister Academic Press. ISBN 978-1-904455-35-6.
^ Lederberg J (1952). "Cell genetics and hereditary symbiosis". Physiol. Rev. 32 (4): 403–430. PMID 13003535.
^ Sinkovics, J; Harvath J, Horak A. (1998). "The Origin and evolution of viruses (a review)". Acta microbiologica et immunologica Hungarica (St. Joseph's Hospital, Department of Medicine, University of South Florida College of Medicine, Tampa, FL, USA.: Akademiai Kiado) 45 (3–4): 349–90. ISSN 1217-8950. PMID 9873943.
^ ^a ^b Russell, David W.; Sambrook, Joseph (2001). Molecular cloning: a laboratory manual. Cold Spring Harbor, N.Y: Cold Spring Harbor Laboratory.
^ Kandavelou K; Chandrasegaran S (2008). "Plasmids for Gene Therapy". Plasmids: Current Research and Future Trends. Caister Academic Press. ISBN 978-1-904455-35-6.
^ Gerdes K, Rasmussen PB, Molin S (1986). "Unique type of plasmid maintenance function: postsegregational killing of plasmid-free cells". Proc. Natl. Acad. Sci. U.S.A. 83 (10): 3116. doi:10.1073/pnas.83.10.3116. PMC 323463. PMID 3517851. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=323463.
^ Kroll J, Klinter S, Schneider C, Voß I, Steinbüchel A (2010). "Plasmid addiction systems: perspectives and applications in biotechnology". Microb Biotechnol. 3 (6): 634–657. doi:10.1111/j.1751-7915.2010.00170.x. PMID 21255361.

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plasmid

plas·mid

plasmid

Plasmid

Plasmid

plasmid

plasmid

plasmid

plasmid

categories related to 'plasmid'

Plasmid

Vectors

Applications

Disease models

Gene therapy

Episomes

Types

Yeast plasmids

Plasmid DNA extraction

Conformations

Simulation of plasmids

See also

References

Further reading

Episomes

External links