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MICROM Exam 2

Terms in this set (24)

Why does a virus need a host cell?
Need host cell to replicate
What is the difference between a productive and a latent infection?
Productive- results in the formation of new viral particles
Latent- virus nucleic acid integrates into host genome or replicates as a plasmid
Why are phages important?
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How is the genome of a virus sometimes different from that of a cell?
Some viral DNA can be single-stranded
How do viruses attach to host cells?
spikes on virion attach to specific host cell receptors
How is the penetration step in the replication of phages different from that of animal viruses?
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How does a temperate phage differ from a lytic phage?
Temperate- have the option of either direction lytic infection (productive) or incorporating their DNA into the host cell genome
Lytic- exit the host cell at the end of the infection cycle by lysing the cell; viral infections result from the formation of new viral particles
What would be the consequence if a temperate phage lost the ability to synthesize a repressor?
It would not be able to exist in the lysogenic state because there would be nothing stopping the expression of the gene for excision
Describe why phages are important to humans.
The virus can "hide" in human cells
What is lysogenic conversion? Give an example.
A change in the phenotype of a lysogen as a consequence of the specific prophage it carries
Lysogen
infected cell in which viral DNA has been incorporated into the host genome
Prophage
the integrated viral DNA that's replicated along with the host cell chromosome
How are phages grown in the lab?
Bacteriophages- lawn of host cells; plaques indicate where bacteriophage is deposited
What is reverse transcriptase and what group of viruses encodes it?
Retroviruses use to convert RNA to DNA by making a single stranded DNA from RNA & hen making the complement to integrate into the host genome
Why are virally encoded polymerases significant medically?
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What is a retrovirus?
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What groups of viruses need to carry their own polymerase within the virion? Why?
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What is an acute infection?
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How is a latent infection different from a chronic infection?
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How are animal viruses grown in the lab?
tissue culture
Transformation, transduction, and conjugation
Transformation- bacterial DNA is transferred as "naked" DNA,
Conjugation- donor cell physically contacts the recipient cell
Transduction- bacterial DNA is transferred inside a phage coat (via bacteriophage)
Why do we assume that colonies growing in figure 8.18a are recombinants and not mutants?
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Which mechanisms of horizontal gene transfer require homologous recombination?
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What is a "competent cell"?
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