Portage Microbiology Module 6 Exam Questions and Correct Answers Latest Update Already Passed

Portage Microbiology Module 6 Exam Questions and Correct Answers Latest Update Already Passed Virus - Answers non-cellular, non-living infectious agent with its own genome. They are obligate intracellular parasites. Virus components - Answers 1. Genomic material 2. Capsid Capsid - Answers membrane-like protein structure containing the virus's genetic material (similar to a cell's nucleus) Envelope - Answers an additional outer membrane surrounding the capsid, derived from the host cell's plasma membrane taken as virus "buds" from host cell. Found in a majority of animal viruses. Naked virus - Answers non-enveloped; host cell bursts as virus lyses from cell. Majority of bacteriophages. Paramyxovirus - Answers Enveloped, 100-150 nm diameter, spherical. Single stranded linear genome fuses with the host cell membrane to initiate entry and replication. (Measles and mumps) Orthomyxovirus - Answers Similar to paramyxovirus but contains eight segments of RNA and enters the host via endocytosis (influenza) Number of viruses known to infect mammals - Answers 5,000 Number of viruses known to infect humans - Answers 220 Estimated number of uncharacterized viruses - Answers 300,000 Virion - Answers a single virus particle with a capsid and genetic material Capsid structures - Answers helical, icosahedral, complex Viral spikes - Answers glycoprotein extensions that identify and bind to host cell proteins. Can be changed by mutating genomes Purpose of viral genome - Answers To encode proteins necessary for capsomere, spikes, and enzymes for replication DNA viral genome - Answers -Can be circular or linear -Often double stranded -May be single stranded RNA viral genome - Answers -Can be linear or segmented -Often single stranded -May be double stranded Human genome size - Answers 3 billion base pairs; 25,000 genes Viral genome size - Answers 7700-2.5 million base pairs; 300 genes Central dogma of biology - Answers DNA is transcribed into mRNA, which is translated by ribosomes into making proteins Protein encoding for double-stranded viral DNA - Answers Same as for cells; DNA-->transcription-->mRNA-->protein Protein encoding for single-stranded viral DNA - Answers Complementary DNA is built-->transcription-->mRNA-->protein Protein encoding for ssRNA+ viruses - Answers mRNA-like genome is immediately ready for translation. (polio, rubella, West Nile encephalitis) Protein encoding for ssRNA- viruses - Answers Genome is complementary to mRNA. Transcription by RNA-dependent RNA polymerases-->mRNA-->proteins (influenza, measles, ebola, rabies) Protein encoding for retroviruses - Answers mRNA-like genome is converted to DNA form by reverse transcriptase--->DNA is inserted in host cell's genome-->transcription-->mRNA-->protein (HIV) Protein encoding for dsRNA viruses - Answers Double-stranded RNA is unwound by RNA-dependent RNA polymerase to single-stranded mRNA-->protein Viral replication - Answers When virus uses the host cell's resources (amino acids, nucleotides, enzymes, and organelles) to make new virions 6 steps to viral replication - Answers 1. Attachment 2. Entry 3. Uncoating 4. Replication 5. Assembly 6. Release Attachment - Answers Virus attaches to host cell via capsid proteins for naked viruses or spike proteins for enveloped Entry by fusion - Answers In enveloped viruses only. Virus binds to receptors on host cell membrane and fuses with it. Host cell cytoplasmic enzymes break down viral capsid and the viral genome is released. Entry by endocytosis - Answers In enveloped or naked viruses. Virus binds to receptors on host cell membrane. Virus is engulfed into endocytic vesicle, enzymes break down capsid and genome is released Uncoating - Answers Breaking down the capsid to release viral proteins and genome Replication - Answers Virus synthesizes its genome and transcribes mRNA to translate viral proteins Assembly - Answers capsids form around viral genome Release - Answers virions either bud off host cell, creating their envelope or they lyse the cell creating naked virions Tropism - Answers Specificity of a virus to bind to its host cell. Ebola has broad tropism Acute viral infection - Answers replication peaks quickly, immune system fights it off, and the infection ends Latent persistent infection - Answers Replication peaks and declines but immune system can't clear it. Quiet periods are when replication is low. Chronic persistent infection - Answers replication is initially low and a person can be asymptomatic but infectious. Virion replication ramps up after several years. (HIV) Provirus - Answers Made when reverse transcripted DNA is inserted in host cell genome, provirus is then transcribed to make the viral genome Number of viral particles that can be produced from a single infected cell - Answers Up to 10,000 Phage - Answers Virus that only infects bacterial cells Significance of bacteriophages - Answers -They can introduce new genetic information and genetic combinations into human microflora -Could be used against antibiotic resistant bacteria, since some can kill prokaryotic cells -Can be used in lab and molecular biology since they have the ability to insert new genetic material