MICRO 3050- VIROLOGY EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED

MICRO 3050- VIROLOGY EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED Leave the first rating Terms in this set (34) What is a virus? What are the two basic components of the extracellular form of a virion? Genetic elements that replicate independently of a cell's chromosome, but requires a living host to replicate -nucleic acid surrounded by protein coat Nucleocapsid Nucleic acid with a protein coat (aka capsid) What makes up an envelope? Lipid bilayer and envelopes can sometimes have structures added on like a spike Describe the four virus capsid symmetries 1. Helical- DNA/RNA of virus coils and capsomeres (capsid) loops around to form a tube shape 2. Icosahedral- geometric shape and most efficient way to close space 3. Vaccinia- oval shape and uncommon 4. Binal Symmetry- icosahedral head and helical tail What's the difference between an envelope and capsid? A capsid is a vital part of the virion and is the protein coat the surrounds the DNA/RNA. The envelope comes from a host's membrane and is made up of lipids, but is an optional addition to the virus. What's the difference between positive and negative sense viruses? Positive- viral genome and mRNA of host cell is the same so the ribosomes can read it Negative- genome and mRNA are opposites so the viral genome must translate itself so it can be read by ribosomes What are the two pathways a virus can use it's positive sense RNA to make protein? 1. RNA genome (+) → DNA (-) → mRNA (+) → protein Do most animal or bacteria viruses tend to have viral envelopes? Animal viruses What is a viral envelope? The outer, flexible, membranous layer made of lipids and carbohydrates that are usually taken from the host What are the six overall steps for viral replication? 1. Attachment to correct host cell 2. Entry into host cell (either fusion with membrane, injecting, or fake phagocytosis) 3. Uncoating of genome 4. Synthesis of virions genome 5. Assembly 6. Release Based on the growth curve graph of viral replication, what are the three steps/periods? 1. Latent period where no actual viruses are in the cell until virions are released extracellularly 2. Eclipse period is when the viral genome has infected the host cell, but no full viruses are made. 3. Process after eclipse where unpackaged virions are now packaged infections viruses Are bacteriophages naked or enveloped? What does their genome look like? Most are naked and contain dsDNA Describe virulent/lytic phages and what is an example phage? They multiply immediately after entering host. When fully mature, they lyse the host, ending in immediate cell death Ex.- T4 What bacteria does T4 infect? How does it inject it's genome into this bacteria? E. coli The tail feet recognize the LPS of the outer membrane, while the tail pins help latch onto the cell. DNA is then injected through the tail tube past the outer membrane, peptidoglycan, and into the cytoplasmic membrane. The site of tail lysozyme helps break up the peptidoglycan What are the importance of new sigma factors for the T4 virus? What happens after the viral genome is in the host cell? New sigma factors (life jacket lookin things) alter E. coli's RNA polymerase so that it only produce viral mRNA - replicate phage DNA, package into phage head proteins, and produce other essential parts to create a mature T4 virion What is the average amount of T4 virions released and how long does it take between the time the bacteria is infected to when it lyses? ~100 and 25 minutes