LIFE 120 Lecture Notes - Lecture 17: Rna Virus, Dna Virus, Lysogenic Cycle
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A virus is an infectious particle consisting of little more than genes packaged into a protein coat. Viruses lead (cid:862)a ki(cid:374)d of (cid:271)orro(cid:449)ed life,(cid:863) existing in a shady area between life-forms and chemicals. Even the largest known virus is barely visible under the light microscope. A typical diameter of virus particle is about 100 nm (100x10-9 m or 0. 1x10-6 m). The length of an e. coli is (cid:1006) (cid:373) ((cid:1006)(cid:454)(cid:1005)(cid:1004)-6 m) Viruses are not cells but are a nucleic acid molecule enclosed in a protein coat. Depending on its type of nucleic acid, a virus is called a dna virus or an rna virus. A capsid is the protein shell that encloses the viral genome. Capsids are built from protein subunits called capsomeres. Some viruses have membranous envelopes that help them infect hosts. These viral envelopes are deri(cid:448)ed fro(cid:373) the host (cid:272)ell"s (cid:373)e(cid:373)(cid:271)ra(cid:374)e a(cid:374)d (cid:272)o(cid:374)tai(cid:374) a combination of viral and host cell molecules.
