COMMON RNA VIRUSES 1. Picornaviridae---these are the smallest viruses and are named with the prefix pico--- (meaning small) plus RNA. Poliovirus is an example. Their kind of RNA is called sense strand RNA or + strand RNA, because it can act directly as mRNA. After attachment, penetration, and uncoating are completed, the single-stranded viral RNA acts directly as mRNA. It is translated into proteins which inhibit the host cell’s synthesis of RNA and protein and an enzyme called RNA-dependent RNA polymerase. (Remember, usually when we make RNA we are using DNA as the pattern, so the enzyme is DNA-dependent RNA polymerase). This enzyme catalyzes the synthesis of a strand of RNA which is complementary to the original viral DNA, and is called the antisense or - strand. The antisense strand will be used to synthesize additional + strands.
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