2604-Sp08-14s - Lecture #14 Viruses March 24th, 2008...

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Lecture #14 Viruses March 24 th , 2008 General Properties of Viruses Replication of Viruses and Measurement of Growth Temperate Viruses Animal Virus Examples Non-Viral Self-Replicating Particles
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The Baltimore Classification Scheme
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Replication of DNA Viruses
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RNA Virus Replication
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Retroviruses and Class VII Viruses Need Reverse Transcriptase Reverse Transcriptase (RT) uses an RNA molecule as template to produce a DNA molecule RT is needed by Retroviruses to make a DNA intermediate as the packaged RNA genome is unable to act as mRNA. RT is needed by Class VII (DNA) viruses which replicate their genomes via an RNA intermediate. Isn’t evolution amazing?
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Concept Check Questions Why must some types of virus contain enzymes in the virion in order for mRNA to be produced? Distinguish between a positive-strand RNA virus and a negative-strand RNA virus. Both plus strand viruses and retroviruses contain plus configuration RNA genomes. Contrast mRNA production in these two classes of viruses.
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Overview of Bacterial Viruses What is thought to be the most common type of bacteriophage genome?
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Bacteriophage T4: a Model for Viral Genetics 5-hydroxymethyl cytosine is substituted for cytosine. This base is glucosylated, rendering T4 DNA resistant to most restriction endonucleases. DNA replication results in circular permutation of the packaged genomes
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Circular Permutation of T4 DNA Replicated genomes are joined to form a large concatemer. The concatemer is cleaved into “headfuls” of DNA, resulting in repeated terminal sequences.
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Events During T4 Infection Elements of transcriptional control Early genes are transcribed directly by host RNApol-σ 70 . Phage- encoded anti-sigma shuts down early mRNA synthesis. Middle genes
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2604-Sp08-14s - Lecture #14 Viruses March 24th, 2008...

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