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EBio - notes7 - Viruses Bacteria Notes 11-29

EBio - notes7 - Viruses Bacteria Notes 11-29 - •Bacteria...

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Vocabulary Lytic, lysogenic, capsid, viral envelopes, prophage DNA virus, RNA virus Prions Transformation, tranduction, conjugation Figures: 18.6, 18.7, 18.8 CONCEPTS: Viruses are different & have a variety of different type of genomes Viral life cycles: lytic & lysogenic Bacteria can obtain new genetic information in a variety of ways: conjugation, transformation, transduction Viruses are not cells •Viruses are very small infectious particles consisting of genome enclosed in a protein coat and, in some cases, a viral envelope Are obligate intracellular parasites Viral genomes may consist of Double- or single-stranded DNA Double- or single-stranded RNA Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus Viruses have two reproductive mechanisms: the lytic cycle and the lysogenic cycle
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The lytic cycle culminates in the death of the host cell •The lytic cycle produces new phages and digests the host’s cell wall, releasing the progeny viruses
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Unformatted text preview: •Bacteria have defenses against phages, including enzymes that recognize and cut up phage DNA The lysogenic cycle replicates the phage genome without destroying the host •The viral DNA molecule is incorporated into the host cell’s chromosome: prophage •Every time the host divides, it copies phage DNA and passes copies to daughter cells Prions are slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals – Prions propagate by converting normal proteins into the prion version – Mad cow disease, scrapie Transduction Transformation and Conjugation are all mechanisms for genetic transfer in bacteria: – In the process known as transduction , phages carry bacterial genes from one host cell to another – Transformation is the uptake of naked, foreign DNA from the surrounding environment – Conjugation is the direct transfer of genetic material between bacterial cells that are temporarily joined...
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