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Unformatted text preview: The envelope of certain viruses is a lipid bilayer containing glycoproteins embedded in the lipid. The envelope gives a somewhat circular appearance to the virus and does not contribute to the symmetry of the nucleocapsid. Projections from the envelope are known as spikes. The spikes sometimes contain essential elements for attachment of the virus to the host cell. The virus of AIDS, the human immunodeficiency virus, uses its spikes for this purpose. Bacteriophages are viruses that multiply within bacteria. These viruses are among the more complex viruses. They often have icosahedral heads and helical tails. The virus that attacks and replicates in Escherichia coli has 20 different proteins in its helical tail and a set of numerous fibers and pins. Bacteriophages contain DNA and are important tools for viral research. Viral replication. During the process of viral replication, a virus induces a living host cell to synthesize Viral replication....
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