QUESTIONS AND ANSWERS SURE A+
✔✔Virus definition - ✔✔Obligate intracellular particle with genetic material + protein
coat
✔✔Virion - ✔✔Extracellular infectious virus particle
✔✔Capsid - ✔✔Protein coat protecting genome
✔✔Envelope - ✔✔Lipid layer aiding entry and protection
✔✔Spikes/glycoproteins - ✔✔Attach to host receptors
✔✔Viral genome - ✔✔DNA or RNA
✔✔Enveloped virus - ✔✔Has lipid membrane; less stable
✔✔Nonenveloped virus - ✔✔No membrane; more resistant
✔✔Viral life cycle steps - ✔✔Attachment, entry/uncoating, synthesis, assembly, release
✔✔Attachment - ✔✔Binding to host receptor
✔✔Entry/uncoating - ✔✔Genome enters cell; capsid removed
✔✔Synthesis - ✔✔Viral replication and protein production
✔✔Assembly - ✔✔New virions formed
✔✔Release - ✔✔Lysis or budding
✔✔Lysis - ✔✔Cell bursts to release virus
✔✔Budding - ✔✔Virus exits without killing cell
✔✔Virulent phage - ✔✔Lytic cycle only
✔✔Temperate phage - ✔✔Lysogenic + lytic cycles
✔✔Lysogenic conversion - ✔✔New traits from prophage (often virulence)
✔✔Virus cultivation - ✔✔Cell culture, eggs, live animals
, ✔✔ Griffith's experiment - ✔✔Used Streptococcus pneumoniae; heat-killed S + live R
killed mouse; showed transforming principle transfers genetic information
✔✔Avery, MacLeod, McCarty - ✔✔Used enzymes to destroy molecules; only DNase
stopped transformation; proved DNA is genetic material
✔✔Hershey-Chase experiment - ✔✔S35 protein stayed outside; P32 DNA entered
cells; DNA is hereditary material
✔✔DNA vs RNA - ✔✔DNA: deoxyribose, A T G C, double-stranded; RNA: ribose, A U
G C, single-stranded
✔✔Phosphodiester bond - ✔✔Links nucleotides; 5' phosphate to 3' OH
✔✔Peptide bond - ✔✔Links amino acids in proteins
✔✔DNA replication phases - ✔✔Initiation, elongation, termination
✔✔DNA polymerase requirements - ✔✔Template, primer (3' OH), dNTPs; synthesizes
5'→3'
✔✔Replication fork - ✔✔Leading strand continuous; lagging strand discontinuous
(Okazaki fragments); ligase joins fragments
✔✔Bacterial gene structure - ✔✔Promoter (-35, -10), transcription start site, coding
region, terminator
✔✔Operon - ✔✔Multiple genes under one promoter; polycistronic mRNA
✔✔RNA polymerase holoenzyme - ✔✔Core enzyme + sigma factor; sigma helps initiate
transcription
✔✔Transcription phases - ✔✔Initiation, elongation, termination
✔✔Sigma factor - ✔✔Recognizes promoter and recruits RNA polymerase
✔✔Factor-independent termination - ✔✔Hairpin loop in RNA stops transcription
✔✔Rho-dependent termination - ✔✔Rho protein terminates transcription
✔✔Reading frame - ✔✔Groups of 3 nucleotides; shift changes entire protein
✔✔Genetic code - ✔✔3-base codons; degenerate; universal; AUG start codon