19_Lectures_PPT_2008_class-1

19_Lectures_PPT_2008_class-1 - Chapter 19 Viruses 0.5 m...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
0.5 µm Chapter 19 Viruses
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Summary Concept 18.1: A virus consists of a nucleic acid surrounded by a protein coat Concept 18.2: Viruses reproduce ONLY in host cells Concept 18.3: Viruses, viroids, and prions are formidable pathogens in animals and plants
Background image of page 2
A borrowed life Viruses called bacteriophages can infect and set in motion a genetic takeover of bacteria, such as Escherichia coli E. coli and its viruses are called model systems because of their frequent use by researchers in studies that reveal broad biological principles the field of molecular biology essentially began in these systems But are they ALIVE? Historically they were thought to be biological chemicals, e.g. the latin root word for virus means ‘poison’
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Bacterial cells are much smaller and more simply organized than those of eukaryotes. Viruses a re smaller and simpler than bacteria Overview: Microbial Model Systems Virus Bacterium Animal cell Animal cell nucleus 0.25 µm
Background image of page 4
Concept 18.1: A virus consists of a nucleic acid surrounded by a protein coat Scientists detected viruses indirectly long before they could see them The story of how viruses were discovered begins in the late 1800s with Tobacco Mosaic Virus (TMV)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
TMV phenotype
Background image of page 6
The Discovery of Viruses: Scientific Inquiry Tobacco mosaic disease stunts growth of tobacco plants and gives their leaves a mosaic coloration In the late 1800s, researchers hypothesized that a particle smaller than bacteria caused the disease they showed that the sap from the diseased tobacco plant was sufficient to spread the disease 1883 Adolf Mayer 1893 Dimitri Ivanowsky 1898 Beijernick In 1935, Wendell Stanley confirmed this hypothesis by crystallizing the infectious particle, now known as tobacco mosaic virus (TMV) this type of crystallography is not possible for bacteria, so it was unclear what these things were. ....then. ...
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Fig. 19-2 RESULTS 1 2 3 Extracted sap from tobacco plant with tobacco mosaic disease Passed sap through a porcelain filter known to trap bacteria Rubbed filtered sap on healthy tobacco plants 4 Healthy plants became infected
Background image of page 8
Structure of Viruses Viruses are not cells Viruses are very small infectious particles consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope They are not metabolically active without a host some are smaller than a ribosome, some are much bigger
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Viral Genomes Viral genomes may consist of Double- or single-stranded DNA Double- or single-stranded RNA Can be a few as four genes or as many as several hundred Depending on its type of nucleic acid, a virus is called a DNA virus or an RNA virus E.coli can be infected by all all classes
Background image of page 10
Types of coli-phage
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Capsids and Envelopes A capsid i s the protein shell that encloses the viral genome A capsid can have various structures commonly the 20-sided shape, icosahedral Greek: eikosaedron, from eikosi (twenty) and hedron (seat)
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/27/2011 for the course BISC 120 taught by Professor Webb,wetzer,? during the Fall '07 term at USC.

Page1 / 44

19_Lectures_PPT_2008_class-1 - Chapter 19 Viruses 0.5 m...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online