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Virus definition
a. Viruses are smaller and simpler and lack structures and metabolic machinery found in a cell; it is an infectious particle consisting of little more than genes packaged in a protein coat
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Are they living or nonliving?
- i. Researchers thought they were the simplest of living forms
- ii. However, they can’t reproduce or carry out metabolic activities outside of a host cell= not alive
- 1. “lead a kind of borrowed life”
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a. Viruses have unique genetic mechanisms that help understand and develop techniques that enable __of genes
manipulation
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a. Viruses detected indirectly
i. __
1. Stunts growth of tobacco plants and leaves their leaves a mosaic of colors
Tobacco mosaic disease
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Adolf Mayer
- i. Discovered he could transmit the disease from plant to plant by rubbing diseased sap onto healthy plants
- 1. Assumed it was bacteria
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Dimitri Ivanowsky
i. Tested hypothesis of it being bacteria by passing sap through filter to remove bacteriaà disease still resulted; still convinced that it was bacteria
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a. Martinus Beijerink
- i. Carried out experiment showing that infectious agent in filtered sap could replicate
- 1. Pathogen replicated only within the host infected
- a. Mysterious agent could not be cultivated
- ii. Credited with being the first scientist to detect viruses
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Wendell Stanley
confirmed his suspicion when he crystallized the tobacco mosaic virus (TMV)
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a. Structure
i. Tiniest: __nm
ii. __particle consisting of __ enclosed in a __ and, for some viruses, surrounded by a __
- 20
- Infectious
- nucleic acid
- protein coat
- membranous envelope
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a. Viral Genomes
i. Their genomes may consist of __(4)__
ii. Called __virus or __virus, based on type of nucleic acid that makes up its genome
- double-stranded DNA, single-stranded DNA, double-stranded RNA, or single-stranded RNA
- RNA
- DNA
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i. Usually organized as a __or __molecule of nucleic acid, although the genomes of some viruses consist of multiple molecules of nucleic acid
1. Smallest viruses known have only __genes in their genome, while the largest have several hundred to a thousand
2. Bacterial genomes contain about 200 to a few thousand genes
- single linear
- circular
- four
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a. Capsids and Envelopes
i. Protein shell= __
1. What are the shapes?
ii. Built from protein subunits called __
Amount of different kinds of capsomeres are __
- capsid
- Rod-shaped, polyhedral, or more complex
- capsomeres
- small (not numerous)
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i. Rod-shaped= __viruses
1. __have 252 identical protein molecules arranged in a __capsid with 20 triangular facets—__
__viruses
- helical
- Adenoviruses
- polyhedral
- icosahedron
- Icosahedral
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i. Some viruses have __ that aid infection
1. __: membranous envelope that surrounds the __of __viruses and many other viruses
a. Derived from __, contains__; also contain their own __
i. Some viruses carry a few __ molecules within their __
- accessory structures
- Viral envelope
- capsids
- influenza
- membranes of host cell,
- host cells phospholipids and membrane proteins
- proteins and glycoproteins
- viral enzyme
- capsids
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a. __have most complex capsids
i. Their capsids have elongated __heads enclosing their DNA
1. Attached to head is a protein tail piece with fibers by which the phages attach to a bacterium
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Bacteriophages
icosahedral
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