BIO 3153 Lecture Notes - Lecture 8: Tobacco Mosaic Virus, Icosahedral Symmetry, Symmetry

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shween

8 Oct 2021

School

University of Ottawa

Department

Biology

Course

BIO 3153

Professor

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Document Summary

Genetic element that cannot replicate independently of a living (host) cell. Exists outside host and facilitates transmission from one host cell to another. Replication/reproduction occurs only upon infection (entry into host cell) Viruses come in many shapes and sizes. Most viruses are smaller than prokaryotic cells; range from 0. 02 to 0. 3 m. Capsid: the protein shell that surrounds the genome of a virus particle. Nucleocapsid: nucleic acid + protein in enveloped viruses. Envelope proteins attach to and infect animal host cell. Lysozymes hole in cell wall to allow nucleic acid entry. Also lyses bacterial cell to release new virions. Reverse transcriptase: rna-dependent dna polymerase in retroviruses. Rod-shaped viruses (e. g. , tobacco mosaic virus or tmv) Length of virus determined by length of nucleic acid. Width of virus determined by size and packaging of capsomeres. Most efficient arrangement of subunits in a closed shell. Single-stranded may be plus sense (same as mrna) or minus sense (complementary to mrna)

Related Questions

21. Are viruses alive or not? Support your opinion.â¨

22. Describe the basic structure of a virus.â¨

23. What tools are necessary for studying viruses? Why couldnâtvan

Leeuvenhoek observe them in his studies? How can we studyviruses today?

24. Describe how an animal virus infects a host cell (ingeneral)

25. Describe how a bacteriophage infects a host cell. Compareand contrast lytic â¨and lysogenic mechanisms of replication. Why isit an advantage for a virus to be able to have both of thesemechanisms of replication?

26. Where do enveloped viruses acquire their envelope from?

27. What component of the flu virus changes every year? How isthis

advantageous for the virus? How does it affect us?

28. Why do you need a flu shot every year?

29.What components of a host cell are used by viruses duringviral replication?

30. Describe 3 different explanations for the origin ofviruses.

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2.)

a.) Are viruses that infect Archaea different from other bacterial viruses?

Yes, they do not have protein coats because of the extreme conditions where they live.

No, they consist of nucleic acid and protein just like other bacterial viruses.

Yes, the structure of archaeal viruses is always completely different from other bacterial viruses.

Yes, they have only DNA genomes.

b.) Of the following examples, which is not a common part of many viral life cycles?

The pox virus genome is replicated by DNA polymerase.

Adenoviruses attach to the cell and the nucleocapsid is taken up by the cell.

Pox viruses replicate in the cytoplasm of the cell.

Once an adenovirus virion is inside a cell, host RNA polymerases transcribe early genes

c.) Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to cancer. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?

Viral genetic material inserts into a host genome close to the termination sequence, far downstream of the promoter, and causes a silent mutation.

Viral genetic material inserts into a host genome in a repetitive noncoding region.

Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.

Viral genetic material inserts into a host genome and causes a mutation in a promoter, turning off a gene that had previously been turned on.

d.) Which statement describes the difference between the normal neuron protein PrP^C and the pathogenic version PrP^Sc?

PrP^C is just a protein and the PrP^Sc is a protein with nucleic acid inside.

The PrP^C protein contains more beta sheets while the PrP^Sc protein contains more alpha helices.

The three-dimensional conformation is identical, but the amino acid sequence is different.

The amino acid sequence is identical, but the three-dimensional conformation is different.

What is a virion?Select the answer below.

A. A single virus particle outside a cell.

B. An empty capsid.