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The "early", "middle" (DNA replication), and "late" genes (virus structure), roughly represent the time course of gene expression. [74] Bacteriophage genomes can be highly mosaic, i.e. the genome of many phage species appear to be composed of numerous individual modules. These modules may be found in other phage species in different arrangements.
The phi X 174 (or ΦX174) bacteriophage is a single-stranded DNA virus that infects Escherichia coli. This virus was isolated in 1935 by Nicolas Bulgakov [ 1 ] in Félix d'Hérelle 's laboratory at the Pasteur Institute , from samples collected in Paris sewers.
During fd phage assembly, the phage DNA is first packaged into a linear intracellular nucleoprotein complex with many copies of the phage gene 5 replication/assembly protein. The gene 5 protein is then displaced by the gene 8 coat protein as the nascent phage is extruded across the bacterial plasma membrane without killing the bacterial host.
The 'helper' phage infects the bacterial host by first attaching to the host cell's pilus and then, after attachment, transporting the phage genome into the cytoplasm of the host cell. Inside the cell, the phage genome triggers production of single stranded phagemid DNA in the cytoplasm. This phagemid DNA is then packaged into phage particles.
A prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. [1] Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages.
Electroporation – use of an electrical field to increase cell membrane permeability. Phage therapy – therapeutic use of bacteriophages. Transfection – means of inserting DNA into a cell. Transformation (genetics) – means of inserting DNA into a cell. Viral vector – commonly used tool to deliver genetic material into cells.
(The DNA must be linear to fit into a phage head.) The cosB site holds the terminase while it is nicking and separating the strands. The cosQ site of next cosmid (as rolling circle replication often results in linear concatemers ) is held by the terminase after the previous cosmid has been packaged, to prevent degradation by cellular DNases .
The first recombinant DNA molecule was created by Paul Berg in 1972 when he combined DNA from the monkey virus SV40 with that of the lambda phage. [ 12 ] Experiments on hereditary material during the time of the Hershey–Chase experiment often used bacteriophages as a model organism .