BS 161 1st Edition Lecture 36 Outline of Last Lecture I. VirusesOutline of Current Lecture II. Viruses continuedCurrent Lecture-lysogenic cycle: replicates the phage genome without destroying the host-prophage: intergrated viral DNA-temperate phages: phages that use both the lytic and lysogenic cycles-many viruses that infect humans have a membranous envelope-viral glycoproteins on the envelope bind to specific receptor molecules on the surface of a host cell-viral glycoproteins are synthesized in the rough endoplasmic reticulum-retroviruses: use reverse transcriptase to copy their RNA genome into DNA-HIV is the retrovirus that causes AIDS-reverse transcriptase: RNA dependent DNA polymerase-HIV infects immune system T cells-AZT: inhibitor of reverse transcriptase-treatment for HIV-HIV evolves and renders AZT useless fairly quickly-provirus: viral DNA that is integrated into the host genome-remains a permanent resident of the host cell-unlike a prophage-the host’s RNA polymerase transcribes the proviral DNA into RNA molecules-the RNA molecules function both as mRNA for synthesis of viral proteins and as genomes for new virus particles released from the cell-since viruses can reproduce only within cells, they probably evolved as bits of cellular nucleic acid-candidates for the source of viral genomes are plasmids, circular DNA in bacteria and yeasts, and transposons, small mobile DNA segments-plasmids, transposons, and viruses are all mobile genetic
View Full Document
Unlocking...