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Microorganisms: Viruses Topics in Depth
The United Colours of Virus-tonWe all get sick all the time, and when we do, it's usually due to one of two reasons: you were infected by a bacterium or virus, or because you fell in love with some...
The genomes of viruses are just like every other genome, they contain all the genes necessary to replicate a virus. However, viruses are very lazy, and just use most of the host cell's machinery...
Types of Viral Spread
So, there are a lot of different types of viruses out there (and that's not even including the weird viruses in the ocean that we never see?). But how do we get infected with viruses? There are fou...
Capsids are the protein coat that protects viral genomes. They are made from one or a few proteins that form repeating units that assemble around the genome. The three major types of capsid that pr...
Plant and Fungal Viruses
For the most part, this chapter is going to only talk about animal viruses. "But," you say, "What about those really cool carrot viruses or viruses that infect fungi or bacteria?" Well, calm down....
Viruses that specifically infect bacteria and archaea (the other two domains of life) are called phages (either shortened for bacteriophage or archaeophage).Phage comes from the Greek word for "dev...
For all the variety in viruses that we've talked about, viruses include other virus-like "organisms." We use the term "organism" very liberally because these are essentially just pieces of RNA or p...
Replication Cycle of a VirusThere are three major steps of a virus replication cycle. First, the virus has to get into a cell, then it has to replicate itself, then it has to get out. A virus would...
Viruses are obligate intracellular parasites, which means they have to live inside of a host and steal hosts enzymes to allow replication, like when aliens inhabit the bodies of politicians and run...
Viral Assembly and Exit
If the conditions are right for making viruses, virus proteins are made, but must be assembled into virus particles before being released in the cold dark world. This is a process called "assembly,...
Immune Defense Against Viruses
The Empire Strikes Back: Host Response to Virus Infection Your body doesn't simply sit idly by as viruses come in and kill off all your cells. For millions of years, we have been exposed to vi...
Restriction factors are proteins that block virus infection by restricting its replication progress. These factors are part of the innate immune defense, and mostly block virus infection early in t...
Viral Escape from the Immune System
Why is the innate immune system not very good against virus infections? Because viruses are continuously evolving, so a general defense mechanism like innate immunity won't protect against an agent...
While the immune system does a lot to control virus infections, it obviously doesn't do everything, because we get sick. So, don't go giving it the "World's Greatest Immune System" mug yet. Fortuna...
Believe it or not, vaccines have been around for centuries. Vaccines are therapies that prime the immune system to handle a certain type of virus infection. Vaccination originated through the proce...
Virus ClassificationMany people think that viruses are bacteria and don’t really understand the differences between the two. This situation is even the case for some doctors. Your body registers...
Test Your Knowledge
Virus Classification Questions1. What is the main difference between enveloped and naked virus particles?(A) Enveloped viruses use DNA polymerase to replicate.(B) Naked viruses use DNA polymerase t...
Made From Trees
Best of Dead TreesPrinciples of Molecular Virology. Alan J. Cann, © 2001 Academic PressPrinciples of Virology. S. Jane Flint, L.W. Enquist, Vincent R. Racaniello © 2009 ASM PressFields Virology....
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