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Cosmids are plasmids that incorporate a segment of bacteriophage λ DNA that has the cohesive end site (cos) which contains elements required for packaging DNA into λ particles. Under apt origin of replication (ori), it can replicate as a plasmid.
Cosmids can contain 37 to 52 (normally 45) kb of DNA, limits based on the normal bacteriophage packaging size. They can replicate as plasmids if they have a suitable origin of replication (ori): for example SV40 ori in mammalian cells, ColE1 ori for double-stranded DNA replication, or f1 ori for single-stranded DNA replication in prokaryotes .
PstI cleaves DNA at the recognition sequence 5′-CTGCA/G-3′ generating fragments with 3′-cohesive termini. [1] This cleavage yields sticky ends 4 base pairs long. PstI is catalytically active as a dimer.
In 1938, Craigie and Yen adapted Vi phages by selective propagation and used them at their critical test dilutions to differentiate 11 types of B. typhosus. [19] In 1943, Felix and Callow extended the method to Salmonella paratyphi B . in 1943 and differentiated 12 types with 11 phages. [ 20 ]
The integration of phage λ takes place at a special attachment site in the bacterial and phage genomes, called att λ. The sequence of the bacterial att site is called attB, between the gal and bio operons, and consists of the parts B-O-B', whereas the complementary sequence in the circular phage genome is called attP and consists of the parts ...
The simplest DNA end of a double stranded molecule is called a blunt end. Blunt ends are also known as non-cohesive ends. In a blunt-ended molecule, both strands terminate in a base pair. Blunt ends are not always desired in biotechnology since when using a DNA ligase to join two molecules into one, the yield is significantly lower with blunt ...
Site-specific recombination, also known as conservative site-specific recombination, is a type of genetic recombination in which DNA strand exchange takes place between segments possessing at least a certain degree of sequence homology.
The plaque reduction neutralization test is used to quantify the titer of neutralizing antibody for a virus. [1] [2] The serum sample or solution of antibody to be tested is diluted and mixed with a viral suspension. This is incubated to allow the antibody to react with the virus. This is poured over a confluent monolayer of host cells.