what is a plasmid?

Answer 1

A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication. It is typically circular and double-stranded. It usually occurs in bacteria, sometimes in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae). Size of plasmids varies from 1 to over 400 kilobase pairs (kbp). There may be one copy, for large plasmids, to hundreds of copies of the same plasmid in a single cell, or even thousands of copies, for certain artificial plasmids selected for high copy number (such as the pUC series of plasmids).

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

Answer 2

A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication.

It is typically circular and double-stranded. It usually occurs in bacteria, sometimes in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae). Size of plasmids varies from 1 to over 400 kilobase pairs (kbp). There may be one copy, for large plasmids, to hundreds of copies of the same plasmid in a single cell, or even thousands of copies, for certain artificial plasmids selected for high copy number (such as the pUC series of plasmids).

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

Answer 3

A self-replicating (autonomous) circle of DNA distinct from the chromosomal genome of bacteria. A plasmid contains genes normally not essential for cell growth or survival. Some plasmids can integrate into the host genome, be artificially constructed in the laboratory and serve as vectors (carriers) in cloning.
www.als.net/als101/glossary.asp

Answer 4

Autonomously replicating extra-chromosomal circular DNA molecules, distinct from the normal bacterial genome and nonessential for cell survival under nonselective conditions. Some plasmids are capable of integrating into the host genome. A number of artificially constructed plasmids are used as cloning vectors.

Answer 5

A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication. It is typically circular and double-stranded. It usually occurs in bacteria, sometimes in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae). Size of plasmids varies from 1 to over 400 kilobase pairs (kbp). There may be one copy, for large plasmids, to hundreds of copies of the same plasmid in a single cell, or even thousands of copies, for certain artificial plasmids selected for high copy number (such as the pUC series of plasmids).

Answer 6

Plasmid is an autonomously replicating ,extrachromosomal circular DNA molecule,distinct from the normal bacterial genome
and non-essential for cells survival under non-selective conditions.

Answer 7

plasmid is a extra chromosomal dna
it is mostly used as vectors
plasmid vectors acts as host and carry desired gene to target site.pbr322 is widely used plasmid vector

Answer 8

Small independent circle of DNA : a small circle of DNA that replicates itself independently of chromosomal DNA, especially in the cells of bacteria. Plasmids often contain genes for drug resistance and are used in genetic engineering, since they can be transmitted between bacteria of the same and different species.

Answer 9

A PLASMID is an extranucleoid circular DNA found in bacteria.
it is not vital for the bacteria but is used for producing toxins or for reproduction. it is highly beneficial for us because it can be used for genetic engeneering, bec it can replicate independent of the nucleoid and serves the purpose of producing multiple copies of the required piece of DNA. i hope this bit of info was helpful.

Answer 10

A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication. It is typically circular and double-stranded. It usually occurs in bacteria, sometimes in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae). Size of plasmids varies from 1 to over 400 kilobase pairs (kbp). There may be one copy, for large plasmids, to hundreds of copies of the same plasmid in a single cell, or even thousands of copies, for certain artificial plasmids selected for high copy number (such as the pUC series of plasmids).

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

Plasmid Early History Time-Line:

1903: Walter S. Sutton and Theodor Boveri independently develop the hypothesis that the units of heredity are physically located on chromosomes, thus giving a physical location for heredity.
1910: Thomas Hunt Morgan describes association of heritable properties in Drosophila with a specific chromosome and begins the analysis of genes in the nucleus.
1920s-1940: Embryological observations suggest that there are hereditary determinants in the cytoplasm.
1946: Joshua Lederberg and Edward Tatum report strong evidence for a sexual phase in E. coli K-12.
1949-1951: J. Lederberg and Cavalli and Heslot find that most strains of E. coli will not mate with K-12.
1950: Andre Lwoff and Antoinette Gutmann clarify the nature of phage lysogeny.
1951: Esther Lederberg discovers the lyosgenic bacteriophage lambda in E. coli K-12.
1950s: Respiratory deficient mutants in yeast (petites) are studied by P. Slonimski and B. Ephrussi and are attributed to cytoplasmic hereditary units in the mitochondria. Mutations in Chlamydomonas are attributed to hereditary units in the chloroplasts by R. Sager.
1950-1952: William Hayes suggests that mating in E. coli is an asymmetric (unidirectional) process rather than one analogous to cell fusion and zygote formation in higher organisms.
1952: J. Lederberg reviews the literature on cell heredity and suggests the term"Plasmid" for all extrachromosomal hereditary determinants.
1952-1953: Hayes, and J. Lederberg, Cavalli, and E. Lederberg report that the ability to mate is controlled by a factor (F) that seems to be an infectious particle not associated with the chromosome.
1954: Pierre Fredéricq and colleagues show that colicines behave as genetic factors independent of the chromosome.
1958: François Jacob and Elie Wollman propose the term "Episome" to describe genetic elements such as F, colicine, and phage lambda which can exist both in association with the chromosome and independent of it.
1959: Jacob and Edward Adelberg find that the F-factor can associate with cell genes and identify F-prime factors.
1959: Alfred Kleinschmidt and R. Zahn show that DNA molecules can be studied in the EM by spreading the DNA in protein films on the surface of water.
1960-1961: T. Akiba, T. Koyama, Y. Isshiki, S. Kimua, and T. Fukushima, and T. Watanabe and T. Fukusawa describe multiple drug resistance transferred by an episome designated the R-factor.
1961: Physical experiments involving DNA labeling (either by density [Marmur et al] or radioactivity [Silver and Ozeki]) show that mating in bacteria is accompanied by transfer of DNA from the donor to the recipient.
1962: In a review on episomes, Allan Campbell proposes the reciprocal recombination of circular episome DNA molecules with the chromosomal DNA as a way to physically insert the episome DNA linearly into the chromosome.
1962: Circular DNA is found to actually exist by Walter Fiers and Robert Sinsheimer in the genome of the small phage phi-X174.
1963: Alfred Hershey shows that bacteriophage lambda can form circles in vitro by virtue of its "cohesive ends". Other circular DNAs are also reported: the E. coli genome by John Cairns, and polyoma virus DNA by Renato Dulbecco and Margerite Vogt, and by Roger Weil and Jerome Vinograd.
1967: R. Radloff, William Bauer, and J. Vinograd describe the dye-bouyant density method to separate closed circular DNA from open circles and linear DNA, thus facilitating the physical study of plasmids.
1969: M. Bazarle and D. R. Helinski show that several colicine factors are homogeneous circular DNA molecules.