Search results
Results from the WOW.Com Content Network
The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [14] [15] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
In addition, many important genes of prokaryotes are stored in separate circular DNA structures called plasmids. [54] Like eukaryotes, prokaryotes may partially duplicate genetic material, and can have a haploid chromosomal composition that is partially replicated. [55]
Examples of bacterial species that have been found to possess multiple replicons include Rhodobacter sphaeroides (two), Vibrio cholerae, [3] and Burkholderia multivorans (three). These "secondary" (or tertiary) chromosomes are often described as molecules that are intermediate between a true chromosome and a plasmid and are sometimes called ...
This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses. [3] Synthesis of daughter strands starts at discrete sites, termed replication origins, and proceeds in a bidirectional manner until all genomic DNA is replicated.
[51]: 14.4 Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids, which usually encode only a few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of ...
conjugative - mediate DNA transfer through conjugation and therefore spread rapidly among the bacterial cells of a population; e.g., F plasmid, many R and some col plasmids. nonconjugative - do not mediate DNA through conjugation, e.g., many R and col plasmids. The pBR322 plasmid is one of the first plasmids widely used as a cloning vector.
These methods have resulted in novel perspectives on genetic relationships that previously have only been estimated. [5] A significant achievement in the second decade of bacterial genome sequencing was the production of metagenomic data, which covers all DNA present in a sample. Previously, there were only two metagenomic projects published.
Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, whereas prokaryotes are the organisms that do not have a nucleus enclosed within a membrane. [ 1 ] [ 2 ] [ 3 ] The three-domain system of classifying life adds another division: the prokaryotes are divided into two domains of life, the microscopic bacteria and the ...