Micr 3164 1st Edition Exam # 2 Study GuideLecture 9 - Viruses:Know the Viral ComponentsVirus particle includes a covering and a central core. The covering includes a capsid and sometimes an envelopeThe central core includes nucleic acid molecules (DNA or RNA) and matrix proteins and sometimes enzymesNaked Virus - consists only of a nucleocapsid Capsid - protein shell that surrounds the nucleic acidNucleocapsid - the capsid with the nucleic acidEnveloped Virus - external covering of a nucleocapsid. Usually a modified piece of the host's cell membraneTake a bit of the cell membrane when they are released from a host cellEnveloped viruses can bud from the cell membrane, nuclear envelope, or ERSpikes - on naked OR enveloped viruses. (Viral Attachment) Allow viruses to dock with host cells. Project from the nucleocapsid or the envelopeVirion - a fully formed virus that is able to establish an infection in a host cellHelical Capsid - rod-shaped, bond together to form a series of hollow discs.During the formation of the nucleocapsid, these discs link with others to form a continuous helix where the nucleic strand is coiledNaked Helical Virus - nucleocapsids are rigid and tightly wound. Enveloped Helical Virus - more flexible and have a looser helix. Includes influenza, measles, and rabiesIcosahedral Capsid - 3D, 20-sided figure w/ 12 evenly spaced corners.Naked Icosahedral Virus - you can clearly see the spikes and make out the 3D shapeEnveloped Icosahedral Virus - have the three layers of DNA core, capsid, and then envelopeComplex Capsids - found in the viruses that infect bacteria. May have multiple types of proteins and take shapes that are not symmetrical.These are NEVER enveloped!!!Release - Enveloped has a calm budding off. Naked has a dramatic split Know the Types of Nucleic AcidsDNA Viruses - double stranded, linear/circular/double helix shape. Has ATCG.RNA Viruses - single stranded, has segmented shape, uses positive and negative sense. Has AUCG.Positive Sense RNA - ready for immediate translation. 5'-3'Negative Sense RNA - must be converted before translation can occur. 3'-5'. Uses RDRP!!!Retroviruses - carry their own enzymes to create DNA out of RNAPolymerases - synthesize DNA and RNAReplicases - copy RNAReverse Transcriptase - synthesizes DNA from RNAThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Know the Order of the Viral Life Cycle1. Adsorption - binding to the host cell. A virus can invade its host cell only through making an exact fit with a specific host molecule2. Penetration/Uncoating - cell membrane is penetrated (endocytosis) and the enzymes dissolve the envelope and capsid3. Synthesis - invaded DNA or RNA and replicating itself4. Assembly - mature virus particles are constructed from the growing pool of parts5. Release - viruses are liberated by budding or exocytosisNaked will be released through exocytosis (dramatic split)Enveloped will be released by budding off VAP ImportanceViral Attachment Protein - has spikes. These determine "host range"Make a virus specific for the host cell. If naked, the VAP will be on the capsid. If its enveloped, the VAP will be on the envelopeHost Range - the limited range of cells that a virus can infect Know Types of CPE and TransformationCytopathic Effects - virus-induced damage to the cell that alters its microscopic appearance Inclusion Bodies - compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasmSyncytia - fusion of multiple host cells into single large cells containing multiple nuclei Transformation - effect on the cell caused by oncogenic virusesIncreased rate of growthAlterations in chromosomesChanges in the cell's surface moleculesCapacity to divide for an indefinite periodOncoviruses - viruses capable of initiating tumors Know the Types of Viral InfectionsAcute - severe but lasts a very short time. Example - common coldPersistent - when the virus never completely goes awayExample - chicken poxLatent - "silent or hidden" and can be turned on or off due to a stimulusExample - herpes BacteriophagesLytic Cycle - Viral DNA destroys cell DNA, takes over cell functions and destroys the cellThe virus replicates and produces progeny phagesThere are symptoms of viral infectionLysogenic Cycle - Viral DNA merges with cell DNA and does not destroy the cellThe virus does not produce progenyThere are no symptoms of viral infection PrionsIt is an infectious protein that contains no DNA or RNACauses disease by touching a normal proteinResists denaturation by heat Lecture 10 & 11 - Genetics:DefinitionsGenome - sum total of genetic material of an organism. Exist in the form of chromosomes, some appear as plasmids.Genome of Viruses - can contain either DNA or RNA Chromosome - discrete cellular structure composed of a neatly packaged DNA molecule. Double stranded, circularGene - segment of DNA that contains the necessary code to make a protein or RNA molecule Phenotype - the expression of certain traits, structures or functionsGenotype - the sum of all gene types; an organism's distinctive genetic makeup Know Basic Structure and Bonding of DNADNA Structure - has 2 sugar-phosphate backbones, multiple bases in between. Have an Antiparallel ArrangementHydrogen Bonds - are in between base pairsCovalent Bonds - are between sugar phosphatesNucleotides for DNA - ATCGNucleotides for RNA - AUCGBase Pairing - A&T (or A&U) and C&GCytosine and Guanine - are connected by 3 hydrogen bondsAdenine and Thymine - are connected by 2 hydrogen bondsPyrimidines - CUTPurines - AG Basics of DNA ReplicationEnzymes involved…Helicase - unzipping the DNA helixPrimase - synthesizing an RNA primerDNA Polymerase III - reading each strand 3' to 5' so that adding bases to the new DNA chain will besynthesized (made) in the 5' to 3' order; proofreading the chain for mistakesDNA Polymerase I - removing primer, closing gaps, repairing mismatchesLigase - Final binding of nicks in DNA during synthesis and repair. Links the fragments and closes the gaps in the lagging strand.Topoisomerases I and II - supercoiling and untanglingOrigin of Replication - short sequence rich in A and T. Less energy is required to separate the two strandsHelicases bind the DNA at the Origin of Replication, untwist the helix, break the H bonds, and it results in two separate strandsLeading Strand - continuous, occurs along the 3' to 5' strand direction.