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What is Virus PowerPoint Presentation

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Description : Viruses are non cellular particles made up of genetic material and protein that can invade living cells.

Tags : VIRUS,what is virus,cellular organisms

Published on : Dec 24, 2021 | Views : 1050 | Downloads : 3

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Viruses
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What Is Virus ? 2 Viruses are non cellular particles made up of genetic material and protein that can invade living cells. OR Virus may be defined as a cellular organisms whose genomes consist of nucleic acid and which obligately replicate inside host cells using host metabolic machinery to different extents to form a pool of components which assemble into particles ( called as virion).
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Fundamentally then a Virus is , A package of genetic information protected by a protein shell for delivery into host cell to be expressed and replicated. 3
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Virus Structure 5 Varies in size , shape and symmetry Helical – These viruses are composed of a single type of capsomer stacked around a central axis to form a helical structure, which may have a central cavity, or hollow tube. Icosahedral – Most animal viruses are icosahedral or near-spherical with icosahedral symmetry. Prolate – This is an isosahedron elongated along one axis and is a common arrangement of the heads of bacteriophages.
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Continue… 6 Envelope – Some species of virus envelop themselves in a modified form of one of the cell membranes, either the outer membrane surrounding an infected host cell or internal membranes such as nuclear membrane or endoplasmic reticulum, thus gaining an outer lipid bilayer known as a viral envelope. Complex – These viruses possess a capsid that is neither purely helical nor purely icosahedral, and that may possess extra structures such as protein tails or a complex outer wall.
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Type of Viruses 9 The viruses within these categories share similar characteristics. They’re composed of RNA or DNA, and are coated with either a protein, lipid or glycoprotein. They’re also parasitic, meaning they can’t replicate without a host. Viruses are also the most abundant biological form of life on the planet. While they can’t be cured, a vaccination can prevent their spread.
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Morphology of Viruses 12 Viruses come in many shapes and sizes, but these are consistent and distinct for each viral family. In general, the shapes of viruses are classified into four groups: filamentous, isometric (or icosahedral), enveloped, and head and tail. Filamentous viruses are long and cylindrical. Many plant viruses are filamentous, including TMV (tobacco mosaic virus). Isometric viruses have shapes that are roughly spherical, such as poliovirus or herpesviruses. Enveloped viruses have membranes surrounding capsids. Animal viruses, such as HIV, are frequently enveloped. Head and tail viruses infect bacteria. They have a head that is similar to icosahedral viruses and a tail shape like filamentous viruses.
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History 13 Viruses were first discovered after the development of a porcelain filter—the Chamberland-Pasteur filter—that could remove all bacteria visible in the microscope from any liquid sample. In 1886, Adolph Meyer demonstrated that a disease of tobacco plants—tobacco mosaic disease—could be transferred from a diseased plant to a healthy one via liquid plant extracts. In 1892, Dmitri Ivanowski showed that this disease could be transmitted in this way even after the Chamberland-Pasteur filter had removed all viable bacteria from the extract. Still, it was many years before it was proved that these “filterable” infectious agents were not simply very small bacteria but were a new type of very small, disease-causing particle.
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How does Virus infect? 15 Enters The virus enters the body through the nose, mouth, eyes or the skin. Infects Once inside the body, a virus infects a host cell by injecting its genetic material. Directs The virus will hijack the cell in order to make many copies of itself and to hide from the immune system. Spreads The host cell dies as the virus multiplies and moves into more cells. This is when the body gets sick. Stops The immune system can protect the body from low-level attacks and adapt to viral infections, so that they won't cause disease again or are less severe. Antiviral medications also can help protect against viral diseases.
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EXAMPLE 1 Coronaviruses 18 Coronaviruses are a type of virus. There are many different kinds, and some cause disease. A coronavirus identified in 2019, SARS-CoV-2, has caused a pandemic of respiratory illness, called COVID-19.
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The first case of COVID-19 was reported Dec. 1, 2019, and the cause was a then-new coronavirus later named SARS-CoV-2. SARS-CoV-2 may have originated in an animal and changed (mutated) so it could cause illness in humans. In the past, several infectious disease outbreaks have been traced to viruses originating in birds, pigs, bats and other animals that mutated to become dangerous to humans. Research continues, and more study may reveal how and why the coronavirus evolved to cause pandemic disease. 19
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Symptoms show up in people within two to 14 days of exposure to the virus. A person infected with the coronavirus is contagious to others for up to two days before symptoms appear, and they remain contagious to others for 10 to 20 days, depending upon their immune system and the severity of their illness. 20
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Example 2 Rabies Virus 22 The rabies virus is a Class V virus, with a bullet-shaped protein coat. This virus is made of linear, single-stranded RNA. The rabies virus genome codes for five proteins, from 12,000 nucleotides. Interestingly, the symptoms of rabies in many animals include increased aggression. This trait, caused by where the virus attacks and the damage it does, causes animals to bite other animals more often than they normally would. The assembled rabies virus particles accumulate in the saliva. Thus, when an infected animal bites another one the virus is passed to the new animal.
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23 Rabies virus is almost always fatal in humans, if not treated immediately. Yearly, there are nearly 15 million post-exposure vaccinations given for rabies. The vaccine essentially loads the body with the dead virus, allowing a large immune response against the virus. This can stop the virus before it gets established in the system. If this happens, there is little chance of recovery. Dogs are commonly vaccinated pre-exposure, which provides a general protection to their owners on the chance they are bitten by an animal infected with the virus.
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Example 3 Small pox 24 Smallpox is a double-stranded, 135- to 375-kilobase (kb) DNA virus that replicates in the cytoplasm of the host cell and forms B-type inclusion bodies (Guarnieri bodies). This is in contrast to herpes viruses, which replicate in the nucleus. The orthopoxviruses are among the largest and most complex of all viruses.
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Example 4 Chicken Pox 25 Chickenpox is a highly contagious disease caused by the varicella-zoster virus (VZV). It can cause an itchy, blister-like rash. The rash first appears on the chest, back, and face, and then spreads over the entire body, causing between 250 and 500 itchy blisters.
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