Chapter 19 Lytic vs. Lysogenic What are the main differences between the two cycles Know phage lambda cycles What is a prophage? How is prophage propagated? What could trigger virus to depart from lysogenic cycle? Difference between prophage and provirus Virus Anatomy Capsid and capsomeres Nucleic acid Membranous envelope Where does this envelope come from? What is the envelope made of? Glycoprotiens – virus Receptors – host cell Proteins in the virus (e.g. reverse transcriptase, polymerase) General/Classification Obligate intracellular parasites DNA or RNA genome, Single or double stranded Protein coat and nucleic acid structural components Some have envelopes – these usually infect what organisms? What does the “host range” refer to? Two characteristics used to classify a virus Viruses HIV - Retrovirus Why is HIV retro (what does this mean?) Mode of entry to host cell Host range Be familiar with replication cycle Why is HIV so difficult to treat? Prions What is a prion? What difficulties do we face in trying to treat prion diseases?