Viruses 1 eukaryotic microorganisms and viruses ws 20102011 virus latin. Viruses have an inner core of nucleic acid surrounded by protein coat known as an envelope most viruses range in sizes from 20 250 nm viruses are inert nucleoprotein filterable agents viruses are obligate intracellular parasites. Zika virus structure revealed national institutes of. Selected viral families, viruses and species affected. Irrespective of their shape and size, the ultimate motive of all the virus structure is designed to contain and protect the viral genome and deliver it to a specific host cell for subsequent replication of the virus. Equine herpesvirus 1 equine viral rhinopneumonitis. Learn biology study guide chapter 20 virus with free interactive flashcards. Can viruses and bacteria mutate such that they render. Isohedral viruses such as adeno viruses, sv15, polio viruses and blue tongued viruses are spherical in shape and their surface is a lattice with identical triangular units. Viral structure viruses are minimally composed of a nucleic acid genome dna or rna and a protein coat. Viral specificity refers to the specific kinds of cells a virus can. Viruses are mainly classified by phenotypic characteristics, such as morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause.
A very influential definition of viruses has been that viruses are intracellular obligate parasites, with a strong emphasis on their dependency on a host. Complex viruses these viruses are composed of polyhedral protein shells. Mathematics supports a new way to classify viruses based on structure. Structure, function, and uses molecular cell biology.
Structure and physics of viruses is an interdisciplinary textbook in which the rapidly expanding fields of structural and physical virology are dealt with in an integrated way. Viruses cannot replicate on their own and they need a host cell in order to survive. Many viruses contain an external membrane called an envelope. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The ones that cause massive problems then kill the cellvirus before it replicates. Bacterial classification, structure and function introduction the purpose of this lecture is to introduce you to terminology used in microbiology. Many animal viruses, which include those that infect humans, are icosahedral in shape. Model virus structure shows why theres no cure for common cold. Virus structures most viruses are much smaller than cells the ones shown here are all drawn at approximately 900,000x magni.
From experience, we know that many different elements can contribute to the emergence of a new virus disease. I would link to it and i did once but it was immediately scanned, virus detected. List the types of approaches used to cultivate viruses, noting which types of viruses are cultivated by each method. Outline the events that lead to the formation of a plaque in a lawn of bacterial cells. Written by well respected and experienced virologists, topics include. That is, viruses infect specific cells or tissues of specific hosts, or specific bacteria, or specific plants. Viruses can only reproduce after they have infected host cells. This is actually the basis of evolution by natural selection. These data indicate that sendai virus nucleocapsid assembly occurs in two steps. The man in the street generally considers viruses as the dangerous agents of infectious diseases. Dengue fever virus rhinovirus is one of the causes of the. The virus injects its genetic material into the cell and uses the cells organelles to replicate. The simplest strategy involves wrapping the viral genome in a protein coat or capsid.
A lot of viruses are either helical or icosahedral in shape. Reoviruses have nonenveloped, icosahedral t capsids composed of double protein shell with a complex structure. Introduction virus classification is the process of naming viruses and placing them into a taxonomic system. In order for viral replication to occur, the virus must first infect a host cell. Prevention without knowledge of the agent, based on recognition that survivors of smallpox were subsequently protected against disease inoculation of healthy individuals with dry material from. Advances in virus research, 2, 184 academic press, new york, 1954. Winner of the standing ovation award for best powerpoint templates from presentations magazine.
This requires the uncoating of the viral genetic material before biosynthesis can occur. Decisions on new names, which encapsulate the recognition of natural groups of viruses, evolve slowly. It belongs to the family of picorna viruses rueckert, 1986 and the genus cardiovirus. One group of viruses, the large dna phages, have icosahedral or elongated heads and helical tails. Adobes pdf language can run os functions and privilege escalate through the editor that runs it, to backdoor your computer and do anything. In the case of many animal viruses, the time elapsed from infection to the generation of the first. The viruses may be spherical, rod like, brickshaped b or shaped like a tadpole with a head and slender tail d. Describe three direct counting methods and two indirect counting methods used to enumerate viruses. Viruses make more of themselves, the only known way a virus can make more of itself is by taking over the host cell. One aspect of this concerns the degree of autonomy exhibited by viruses. Antivirals and vaccines are made available to decrease the production of viruses, but not totally stopping them. Three genera exist with this family that pertain to influenza viruses, influenzavirus a, influenzavirus b, and influenzavirus c, each of which contain a single species, or type.
If the virus doesnt develop quicker then their host, the host would develop to where a virus wouldnt be able to take over other cells. Once a virus contacts a suitable host it begins to infect the cell, and. Model virus structure shows why theres no cure for common. I always thought that you could only get a virus from a program file, and pdfs are. If one has to lecture before an assembly of microbiologists. Virology and bacterial genetic recombination a virus is a noncellular entity that can replicate within a permissible host cell. Without a host cell, the virus cannot make more copies of itself. Helical surface symmetry and structure are characteristic of tobacco mosaic virus tmv and animal viruses that cause diseases such as measles, mumps, influenza and rabies. In phage t4, these parts are complemented with other protein complexes forming fibers and other structures. Dimitri ivanowski, a russian botanist in 1892 demonstrated experimentally that sap.
Uncoating of animal viruses unlike bacteriophages, in which only the dna or rna enters the host cell, the capsid of most animal viruses enters the host cell. Choose from 500 different sets of biology study guide chapter 20 virus flashcards on quizlet. The virus have to develop quicker then their host cell. General characteristics, structure and taxonomy of viruses. Zika virus structure revealed at a glance the zika virus surface is similar to that of dengue and related viruses at the nearatomic level, researchers found, but with a notable difference. Helical viruses in these viruses, the nucleic acid genome is wound inside a cylindrical protein capsid with helical symmetry. Viruses of the lytic cycle are called virulent viruses. Human herpesvirus 3 varicellazoster virus chicken pox, shingles. There are 60 copies of each of four different viral proteins vp1, vp2, vp3 and vp4 in its coat.
The dna is injected into the bacteria through the baseplate. For example, the roles of certain cellular factors in initiation. There is an entire class of viruses known as bacteriophages that prey exclusively on bacteria. Virus particles, often termed virions are assembled through two strategies. When a single virus is in its complete form and has reached full infectivity outside of the cell, it is known as a virion. They can be simple or complex in structure, and they have different ways of getting into host cells. In the first stage, called penetration or absorption the virus injects its own genetic material into a host cell causing the infected cell to mistakenly replicate or copy the dna thousands of times. Mathematics supports a new way to classify viruses based. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Mengo virus is a small icosahedral rna animal virus with a molecular weight of 8. Adolf mayer described for the first time a disease of tobacco plant.
Worms and viruses university of california, berkeley. Hiv, the virus that causes the disease aids and is the most famous virus in the world right now, has this basic structure. The authors have attempted to write a book basic enough to be useful to students, as well as advanced and current enough to be useful to senior scientists. Structure of the thermally stable zika virus nature. Viruses are metastable macromolecular assemblies composed of the viral genome enclosed within a proteinaceous coat i. Official approval for new names depends upon a series of sequential steps. Influenza a virus, influenza b virus, and influenza c virus, respectively table 10. Problems and solutions article pdf available in library hi tech news 297. Viruses 3 viral replication strategies the life cycle of most viruses is designed to maximize the production of progeny virus particles.
Each viral particle, or virion, consists of a single nucleic acid, rna or dna, encoding the viral genome. Viruses differ in shape and in ways of entering host cells. The shapes of virus particles or viruses are known chiefly from electron micrographs. Classification of viruses viruses are classified on the basis of morphology, chemical composition, and mode of replication. These viruses appear spherical in shape, but a closer look actually reveals they are icosahedral. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. They are also called icosahedral viruses because of their symmetry. Viruses also often express proteins that modify hostcell processes so as to maximize viral replication. Once a sufficient number of viruses have been replicated, the newly formed viruses lyse or break open the host cell and move on to infect other cells. A virus is an obligate intracellular parasite, meaning that it absolutely must be inside a cell in order for it to replicate.
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