LIFESCI 4 Chapter Notes - Chapter 18.1: Prophage, Reverse Transcriptase, Aids
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18. 1 a virus has a genome but can reproduce only within a host cell it was found by scientists that pathogens actually reproduce only within the host it infects. Dna, double stranded rna, or single stranded rna, depending on the kind of virus. Virus types: rna virus or dna virus. Smallest viruses have only four genes, while largest have several hundred. Capsid: the protein shell enclosing the genome: can be rod shaped, polyhedral, or more complex in shape. Built from large number of protein subunits called capsomeres. Viruses can only reproduce within a host cell. o they lack metabolic enzymes, and ribosomes: each type of virus can infect only a limited range of host cells, called host range. The lytic cycle is a phage reproductive cycle that culminates in death of the host cell. This term refers to the last stage of infection, when the bacterium lyses: a phage that reproduces only by a lytic cycle is a virulent phage.
