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Light Microscopy: Comparison of Optics

Author(s): David R. Caprette, PhD
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What Are Viruses?

Viruses are submicroscopic particles that can be seen only with a powerful electron microscope. They are not cells, but consist of genetic material, either DNA or RNA, that is enclosed in a protective layer of protein. Viruses are able to enter certain host cells and, in fact, must invade a host cell to reproduce. Once inside living cells, viruses hijack cellular apparatuses necessary to make copies of themselves. For this reason, they are considered intracellular parasites. Viruses use the instructions contained in their genomes to produce virus components, both nucleic acid and proteins, which are then assembled to produce new virus particles. The new virus particles then can go on to infect other cells and continue the cycle of virus reproduction.