MIC 205 1st Edition Lecture 15 Outline of Last LectureI. Wrap up Microbial Geneticsa. Translation cont.II. Control Genetic ProcessOutline of Current Lecture III. VirusesIV.Current LectureViruses- Nonliving, acellular, miniscule infectious agento Carry 1 or several pieces of DNA or RNAo Obligate intracellular parasites- Infect bacteria, plants and animals o Not an organismo No cytoplasmic membrane, organells, metabolic functiono Cannot reproduce independently- Viruses ONLY infect ONE particular host organismo Viral proteins are special glycoproteins that must be compatible with the hostStructure of Viruses- If a virus is outside the host it is called a VIRIONo Made up of a protein capsid that carries the nucleic acid- If a virus is inside the host it is a naked nucleic acido The capsid is shedThe Viral Envelope- On some NOT all animal viruseso Composed of phospholipid bilayer and proteinso Viral envelope is acquired from the host cell during viral replication Makes it look like the host cellsThese 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.Categorizing Viruses- Type of genetic material they containo DNA OR RNA (never both) Single or double stranded Circular or linear- Kinds of cells they attack (hosts)- Size and shape of virus- Capsid structure- Presence of envelope or notViral Replication- Depends on the host cell’s organelles and enzymes to produce new virons- Types of replication:o Lytic replication- destructive mechanism that results in death and degradation of host cell (Lysis) ALL viruses do some sort of this replication- Dormancy replication:o Lysogenic replication- extended dormancy replication in bacteriophages o Latent replication- dormancy in animal viruses, can be temporary OR permeantLytic Replication of Bacteriophages- 5 stages1. Attachment (tail fibers)2. Entry3. Synthesis4. Assembly5. Release- Replication cycleo Burst time- period required to do the entire lytic processo Burst size- total number of new virions released Short burst time and large burst size means more infectious virusLysogenic Replication of Bacteriophages1. Attach and entry of lytic cycleo Then it enters dormancy2. Bacterial chromosome and viral genome combine into one loop (Prophage in chromosome)3. Replication of chromosome (copies viral genome at same time)4. Specific conditions allow the prophage to undergo induction, exits dormancy and enters the Lytic cycle at synthesis again**Lysogenic phage must re-enter Lytic Replication in order to go infect a new hostLytic Replication of Animal Viruses- Same pathway as lytic for bacteriophages with same 5 steps as aboveo Differences result from: Prescence of envelope Eukaryotic nature of animal cell hosts Lack of cell wall surrounding animal cell hostsAttachment and Entry of Animal Viruses- Attachment through surface glycoproteins that are complimentaryo Mediated through glycoprotein spikes- 3 entries:o Direct penetration (non-enveloped animal viruses)o Membrane fusion (enveloped virus)- The envelope fuses to the lipid bilayer of the cell membrane and deposits into the cello Phagocytosis (enveloped virus)- A phagocytic cell “swallows” the enveloped virus then the contents are emptied and the capsid is uncoatedSynthesis of Animal Viruses- Each type of animal virus requires different synthesis depending on RNA/DNA and single/double strandedAssembly and Release of Animal Viruses- DNA self assembles in nucleus and released into cytosol- RNA develop solely in cytoplasmLatent Replication of Animal Viruses- Dormancy can be temporary or permanent o Incorporated into the host chromosomes or just sit in the cell- Ex: chicken pox, HIV/AIDS,