It may also be several different proteins, as in the T-even bacteriophages . Images from W.H. Freeman and Sinauer Associates, used by permission. The lysogenic cycle occurs when the viral DNA is incorporated into the host DNA as a prophage. Sometimes the prophage can emerge from the host chromosome and enter the lytic cycle spontaneously once every 10,000 cell divisions. Ultraviolet light and x-rays may also trigger emergence of the prophage.
Transduction is the transfer of host DNA from one cell to another by a virus.
Some bacteriophages are temperate since they tend to go lysogenic rather than lytic. Image from W.H. Freeman and Sinauer Associates, used by permission. Unlike episomes and prophages, transposons contain a gene producing an enzyme that catalyzes insertion of the transposon at a new site. They also have repeated sequences 20-40 nucleotides in length at each end. Complex transposons are much larger and carry additional genes.