Rebecca Davenport Wednesday 10 35 1 15 9 25 16 Ch 19 blueprint 1 Viruses a Characteristics i Smaller than cells ii More simple than cells iii Lack the structures and machinery found in cells 1 Obligate intracellular parasite iv Debate if viruses are alive or not1 Not considered living cause they are A cellular v Host range a virus can only infect a limited number of host species 1 Evolution of recognition systems by the virus b Structure i 20 nm ii Made up of nucleic acid and protein coat aka capsid iii Classify viruses based on nucleic acid capsid structure iv Some viruses have accessory proteins 1 Membranous envelope c Types i Helical Virus looks like a slinky 1 Rod shaped 2 Capsomeres arranged in helical shape 3 Ex tobacco mosaic virus 4 ii Icosahedral virus 1 Polyhedral capsid w 20 trianglular facets isohedron 2 Ex Adenovirus 3 iii Bacteriophage 1 Viruses infect bacteria 2 Ex Bacteriophage T4 3 iv Accessory structures 1 Help infect hosts 2 Mainly made of host cell membrane 3 Ex Influenza Virus d Genetic makeupi Double stranded ii Single stranded iii Double stranded RNA Mutate iv Single stranded RNA Mutate e Capsid protein coat that surrounds and protects genetic material f Viral Replicative Cycle i 1 Don t have to know step 3 what transcription means ii Lytic phages 1 Results in host cell death 2 3 JUST the DNA is injected into the host iii Lysogenic phages 1 Allow replication of phage genome without destroying host 2
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