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Unformatted text preview: Chapter 23 All organisms can independently reproduce and metabolize . Viruses or Virions Pathogens ; agents of infection for disease and illness Viruses are not cells; no plasma membrane Cannot metabolize independently Forces host cells to replicate viral DNA/RNA o Takes over a cells transcription and translation to reproduce itself Strand of DNA or RNA inside a protein coat called a Capsid Genetic info wrapped in protein Phage = virus = bacteriaphage If they are not alive, where did they come from ? Escaped gene hypothesis o DNA fragment that passed through damaged cell membrane o Viruses are often host species-specific o Similarity of virus genome to host genome more similar than between viruses Origin prior to divergence of the three domains o Similarities between protein structures of capsids o Genetic similarities between viruses that infect the Eubacteria and the Archaea o Convergent evolution unlikely If they are not alive, how do they reproduce?...
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