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Partial Diploid Formation (continued) Transduction - Lytic and Lysogenic Infections Lytic Infection Lysogenic Infection integration excision x excision integration prophage • In a lytic infection the bacteriophage binds to the surface of the bacterial cell and injects its DNA. The DNA is replicated and expressed using host cell systems. The DNA and viral proteins assemble into new virus particles. The host cell lyses and the new virus particles are released. • A bacteriophage that can only undergo a lytic infection is said to be virulent. Genetics Handout 27.1 • In a lysogenic infection the bacteriophage binds to the surface of the bacterial cell and injects its DNA. The DNA integrates into the host cell chromosome forming a prophage. The prophage is replicated with the host cell DNA. In some cells the prophage excises and produces a lytic infection. • A bacteriophage that can undergo a lytic or lysogenic infection is said to be temperate. Transduction - Generalized • Virus incorporates random fragment of host cell DNA during assembly. x • On infection fragment is transferred into cell. • DNA fragment can recombine with the bacterial chromosome. x • Any gene can be transferred. • Mapping is possible. Loci that are close together can be transduced together. Loci that are far apart will not fit into virus particle. Transduction - Specialized • Virus incorporates adjacent fragment of host cell DNA during excision. x x • On infection fragment is transferred into cell. • DNA fragment can recombine with the bacterial chromosome. • Only genes flanking the prophage can be transferred. Genetics Handout 27.2