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  Home >> Molecular Biology Dictionary >> Babs -Biosynthetic binding sites bacteriophage

BABS
(biosynthetic antibody binding sites) See dabs.

BAC
1. (bacterial artificial chromosome) A cloning vector constructed from bacterial fertility (F) factors; like YAC vectors, they accept large inserts of size 200 to 500 kb. See cloning vector; YAC.
bacillus A rod-shaped bacterium.
2. A cloning vector capable of carrying between 100 and 300 kilobases of target sequence. They are propagated as a mini­chromosome in a bacterial host. The size of the typical BAC is ideal for use as an intermediate in large-scale genome sequencing projects. Entire genomes can be cloned into BAC libraries, and entire BAC clones can be shotgun-sequenced fairly rapidly.

Bacillus thuringiensis (Bt)
A bacterium that kills insects; a major component of the microbial pesticide industry.

Back mutation
A second mutation at the same site in a gene as the original mutation. The second mutation restores the wild-type nucleotide sequence.

Backcross .
Crossing an organism with one of its parents genetically equivalent organism. The offspring of such cross are referred to as the backcross generation or backcross progeny. See testcross.

Bacteria

1. Plural of bacterium, q.v.
2. One celled microorganisms which do not have a nuclear membrane.

Bacterial toxin

A toxin produced by a bacterium, such as Bt toxin by Bacillus thuringiensis.

Bacteriocide bactericide
A chemical or drug that kills bacterial cells.
Bacteriocin

A protein produced by bacteria of one strain and active against those of a closely related strain.

Bacteriophage
A virus that infects bacteria. Also called simply phage. Altered forms are used in DNA cloning work, where they are convenient vectors. The bacteriophages most used are derived from two "wild" phages, called M13 and lambda. (1). Lambda phages are used to clone segments of DNA in the range of around 10-20 kb.

They are lytic phages, i.e., they replicate by lysing their host cell and releasing more phages, On a bacteriological plate, this results in a small clear zone – a plaque. Some lambda vectors have also been developed which are expression vectors (q.v.). The M13 system can grow inside a bacterium, so that it does not destroy the cell it infect but causes it to make new phages continuously. It is a single stranded DNA phage, and is used for the Sanger di-deoxy DNA sequencing method (see DNA sequencing). Both of these phages grow on Escherichia coli as a host bacterium.

 

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