Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Viral phylodynamics wikipedia , lookup
Virus quantification wikipedia , lookup
Social history of viruses wikipedia , lookup
Oncolytic virus wikipedia , lookup
Bacteriophage wikipedia , lookup
Influenza A virus wikipedia , lookup
Negative-sense single-stranded RNA virus wikipedia , lookup
Introduction to viruses wikipedia , lookup
Plant virus wikipedia , lookup
Chapter 25 Notes Viruses Discovery of Viruses Scientists that helped in the discovery of viruses Martinus beijerinck – studied the tobacco plant are concluded that diseased plants could infect the leaves of healthy plants Dr. Wendell Stanley – (1935) the first to isolate the tobacco mosaic virus and show that it could be crystallized The Nature of Viruses Too small to be seen with a light microscope Viruses are much smaller then bacteria Viruses come in a variety of shapes Composition and Structure ﻻViruses contain genetic material (DNA or RNA) surrounded by a protein coat ﻻGenetic material or nucleic acid is the core and takes many forms (linear, circular, double/single stranded) ﻻProtein coat (CAPSID) – accounts for 95% of a viruses weight Composition and Structure ٭Most common structure is an icosahedron which is a regular figure with 20 triangular faces (looks like a knobby sphere) ٭Another common structure is a helix which appears rod-shaped under the electron microscope Viruses and Life سWhen outside a host cell, a virus shows no signs of life. To become active a virus needs a host cell سViruses are a lot like parasites except they do not depend on their hosts for nourishment because they do not grow Reproduction • Viruses reproduce by taking over a hosts cell’s machinery • In bacteria, viruses inject nucleic acid, the rest stays outside • If a virus attack whole organisms they enter intact once inside their genetic material is released. They then use the organisms ATP for energy and ribosomes to make new proteins which are assembled with genetic material to make new virus particles called virons Production • The production of virons may cause cell death • Viruses attack specific types of cells • Ex – colds invade nose and throat epithelial cells • Polio viruses attacks nerve cells in the brain ad spinal cord Term • Virulence – The ability of a virus to cause serious disease RNA Viruses Some viruses have RNA as it’s genetic material instead of DNA These viruses can still carry out transcription and translation with the use of special enzyme Classification of Viruses Presently viruses are classified according to their size and shape First classified as a DNA or RNA viruses Next subdivided on the basis of shape Next subdivided on the basis of size Bacteriophages • Bacteriophages are viruses that attack bacteria (bacteria eaters of phages) • Structure of Bacteriophages – Nucleic acid core and a protein coat just like all viruses. Six structural types have been identified in their protein coat. They are called T through T6. T is the most studied bacteriophage as they infect the E-coli bacteria. The T – even phages are virulent