Gene that encodes the toxin for cholera is transmitted by: September 2007

Ans. C: Bacteriophage A bacteriophage/phage is a virus that infects a bacterial cell, taking over the host cell's genetic material, reproducing itself, and eventually destroying the bacterium. Bacteriophages have two main components, protein coat and a nucleic acid core of DNA or RNA. Most DNA phages have double-stranded DNA, whereas phage RNA may be double or single-stranded. A filamentous bacteriophage transmits the gene that encodes the toxin for cholera. Cholera toxin genetic element CTX constitutes the genome of a filamentous bacteriophage (CTXf). The phage could be propagated in recipient V. cholerae strains in which the CTXf genome either integrated chromosomally at a specific site, forming stable lysogens, or was maintained extrachromosomally as a replicative form of the phage DNA.