Questions and Answers
During the lysogenic cycle, viral DNA is replicated using the host's cellular machinery without harming the host cell because:
The chemical composition of viral DNA and host DNA is the same, so the host cell machinery cannot distinguish between the two
What distinguishes the lytic cycle from the lysogenic cycle in viral replication?
The lytic cycle involves assembly of new virus particles and release by bursting, leading to host cell death
What is one of the major causes of high infectivity rate of viral diseases among their hosts?
Lytic mode of reproduction of viruses
What is the term for the process in which a bacterium is infected by a temperate or non-virulent phage?
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What triggers the transition from lysogenic to lytic replication cycle in a phage?
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What is the first step in the bacterial lytic infection cycle?
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What term is used to describe the presence of certain prophage-specific genes that can incorporate additional traits in the host bacteria?
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What is the main difference between the lytic and lysogenic cycles of bacteriophages?
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What is the function of tail fibers in the structure of bacteriophages?
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Which statement accurately describes the structure of bacteriophages?
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Study Notes
- Bacteriophages are viruses that specifically infect bacteria.
- Discovered in 1915 by Frederick W. Twort, confirmed by F.D. Herelle in 1917.
- Structure consists of a capsid, nucleic acid genome, sheath, and tail fibers.
- Capsid proteins recognize specific bacterial receptors for attachment.
- Replication happens through lytic or lysogenic cycles.
- Lytic cycle: virus takes over host systems, produces new virions, and kills the host.
- Lysogenic cycle: virus integrates into host genome as prophage, replicates along with host genome, and does not kill the host.
- Lytic cycle has a high yield of viral genomes but kills the host, while lysogenic cycle has a lower yield but establishes a dormant stage.
- Lambda phage is an example of a virus undergoing the lysogenic cycle.
- Phage attaches to host cell, penetrates the cell wall, integrates genome into the host chromosome, and becomes a prophage.
- Lysogenic cycle is a temperate infection and does not kill the host bacteria.
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