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Micro 234 Homework 4 Viruses and Prions
Terms in this set (36)
What characteristics of a virus lead many biologists to conclude that they are non-living biological entities?
Do not reproduce independently, do not metabolize, do not maintain homeostasis, are acellular.
What characteristics of a virus are like those found in living things?
Evolve and adapt.
What structure(s) are common to naked viruses and enveloped viruses?
Both have a nucleocapsid. Both have some type of genetic material
What types of nucleic acids do viruses contain?
Viruses contain either DNA or RNA, but not both. DNA viruses have either ssDNA or dsDNA. RNA viruses contain either ssRNA or dsRNA. ssRNA can be either +ssRNA or -ssRNA
What is the ultimate source of a viral envelope?
A host membrane, such as the cell membrane, or a membrane from the endomembrane system.
What are the basic steps of lytic replication in bacteriophage?
Attachment, Entry, Synthesis, Assembly, Release
What is the fundamental difference between lytic replication and lysogenic replication?
Lysogenic phage can enter the host chromosome and enter a dormant state (lysogeny)
What is lysogenic conversion? Provide an example of lysogenic conversion.
An alteration in bacterial genotype and phenotype due to a prophage. Cholera toxin produced by V. cholerae is encoded by prophage genes.
Compare and contrast the synthesis and assembly stages in the replication of RNA animal viruses and DNA animal viruses.
DNA viruses replicate their DNA within the host nucleus, proteins are synthesized at the ribosomes, and assembly takes place within the nucleus.RNA viruses replicate their RNA in the host cytoplasm, proteins are synthesized at the ribosomes, and assembly takes place in the cytoplasm
Contrast the ways in which animal and bacterial viruses enter their host cells. Explain why the mechanisms are different.
Bacterial viruses must inject their DNA due to the bacterial cell wall. Animal viruses can enter by direct injection, membrane fusion or endocytosis. Membrane fusion and endocytosis cannot occur in bacteria due to the presence of peptidoglycan.
What enzyme, used by the Retroviridae, makes a DNA copy of RNA?
What are the viral features used in viral classification?
Type of nucleic acid, shape of capsid, naked or enveloped
What is the process by which a prophage becomes a lytic phage?
Briefly explain the release of animal viruses from a host cell.
Naked viruses are released by lysis. Enveloped viruses are released by budding or exocytosis
Where in a eukaryotic cell does synthesis of viral proteins take place?
Cytoplasm (at the ribosomes)
Explain why RNA viruses must supply their own replication enzymes.
Eukaryotic cells do not possess enzymes that can read RNA to make an RNA copy.
What diseases do each of the following viruses cause? Zika virus
Oral herpes (cold sores)
Rubella (German measles)
Genital warts, cancer
Why has drinking water treatment and sewage treatment eliminated the transmission of Enterovirus?
Enterovirus is transmitted via the fecal oral route. Treatment of water reduced transmission of the virus.
What types of diseases do prions cause?
Spongiform encephalopathies - BSE, kuru, Creutzfeldt-Jakob disease
How do infectious prions differ from native prions?
Infectious prions possess a β-pleated sheet secondary structure while cellular PrP has an α-helix secondary structure
What makes prions unique when compared to all other disease-causing entities?
Prions do not have any nucleic acid.
Recommended textbook explanations
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
Fundamentals of Biochemistry
Charlotte W. Pratt, Donald Voet, Judith G. Voet
Miller and Levine Biology
Joseph S. Levine, Kenneth R. Miller
Campbell Biology (AP Edition)
Cain, Jackson, Minorsky, Reece, Urry, Wasserman
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