Term
| All viruses have a nucleocapsid. What 2 components do all viruses have in their nucleocapsid? |
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Definition
| Nucleic acid (viral genome) and Capsid |
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Term
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Definition
| The protein coating around the genome, determines the shape of the virus |
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Term
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Definition
| Repeating or identical protein subunits that make up the capsid |
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Term
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Definition
| Classification of viruses based on genome |
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Term
| Primary vs. Secondary characteristics of viruses |
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Definition
Primary~ Genome (how they make mRNA)
Secondary~ Envelope & Shape |
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Term
| Naked vs. Enveloped viruses |
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Definition
Naked viruses~ only nucleocapsid
Enveloped viruses~ nucleocapsid enclosed by lipid bilayer |
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Term
| Naked vs. Enveloped viruses |
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Definition
Naked viruses~ only nucleocapsid
Enveloped viruses~ nucleocapsid enclosed by lipid bilayer |
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Term
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Definition
| Protein layer connecting envelope to nucleocapsid |
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Term
| Why are naked viruses more resistant to disinfectants than enveloped viruses? |
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Definition
| Disinfectants destroy the lipid bilayer of enveloped viruses, which are necessary for attachment to the host cell. Naked viruses are not affected and can still attach to host cells. |
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Term
| Viral attachment proteins def. |
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Definition
| Surface proteins of viruses that determine host range and tissue tropism. They are recognized by the immune system, and viral identification |
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Term
| 3 types of viral attachment proteins & def. |
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Definition
Spike proteins~ glycoproteins on envelopes
Tail fibers~ on a complex phage
Fiber proteins~ on capsid of naked viruses |
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Term
| 4 common shapes for viruses |
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Definition
Icosahedral ~ radial symmetry
Helical/Filamentous ~ flexible
Complex/Amorphous ~ no symmetry
Complex-tailed |
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Term
| 3 parts of complex-tailed bacteriophages |
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Definition
Head~ icosahedral, contains genome
Tail~ injects genome into host cell
Tail fibers~ attachment to host cell |
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Term
| 5 steps of viral replication |
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Definition
1. Host Cell Recognition & Attachment
2. Genome Entry
3. Biosynthesis
4. Assembly/Maturation
5. Release & Transmission |
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Term
| Productive vs. Latent phage growth |
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Definition
Productive~ more virions produced and released
Latent (lysogenic)~ viral genome replicates or integrates as circular DNA, no virions produced |
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Term
| Lytic vs. Temperate phage |
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Definition
Lytic (virulent)~ produced by productive growth
Temperate~ produced by lytic growth, can switch to productive growth |
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Term
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Definition
| A non-cellular particle containing a genome that can replicate only inside the host cell |
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Term
| Bacteriophage (phage) def. |
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Definition
| A virus that infects bacteria |
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Term
| 4 Acellular agents of viruses |
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Definition
-No plasma (cell) membrane
-No binary fission
-No way to generate ATP
-No way to synthesize proteins |
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Term
| What 3 things do Obligate Intracellular Parasites do? |
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Definition
-Uses host cell for energy and substrates
-Hijack the host cell's replication machinery
-Direct host cell to express viral genes and proteins |
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Term
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Definition
| A complete virus particle, not broken down |
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Term
| What is a lysozyme used for in the genome entry step for a complex phage? |
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Definition
| Making a hole in the cell wall to inject the viral genome and not the capsid |
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Term
| Where do viral attachment proteins attach to the cell membrane/wall |
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Definition
| On "receptors" (e.g., LPS, porin, pili) |
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Term
| Early vs. Late genes/proteins |
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Definition
Early genes/proteins~ modify or alter the host's replication or transcription
Late genes/proteins~ rebuild the virus (in complex phage; phage-tail, capsomeres, etc...) |
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Term
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Definition
| The number of virions released from a host cell (usually in the hundreds) |
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Term
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Definition
| Clearing on a lawn of bacteria on an agar plate that shows phage infection occurred (lysis or no growth) |
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Term
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Definition
| A temperate phage that integrates its genome into the host bacterial cell. |
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Term
| What do prophages do to the host cell? |
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Definition
| They give the host cell new properties (phenotypes) |
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Term
| 2 types of bacterial defense against phage & how they work |
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Definition
Restriction enzymes~ recognize short DNA sequences and cut foreign DNA (uses methylation)
CRISPR~ crRNA is transcribed from integrated phage sequences in their own genome, CAS proteins cleave DNA, and bacteria target the invading phage DNA sequence. |
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Term
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Definition
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Term
| 2 types of genome entry that often involve the entire nucleocapsid |
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Definition
Endocytosis (by host)~ virus-host attachment triggers endosome formation, the only option for naked viruses
Fusion~ envelope fused with host plasma membrane |
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Term
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Definition
| Capsid is broken down to release the genome once inside the host |
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Term
| Biosynthesis makes what 2 things? |
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Definition
| Viral genome and virus proteins, mechanisms depend on the viral genome |
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Term
| DNA Polymerase template & product |
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Definition
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Term
| RNA Polymerase template & product |
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Definition
| DNA -> RNA (transcription) |
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Term
| Replicase template & product |
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Definition
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Term
| Reverse Transcriptase template & product |
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Definition
| RNA -> DNA (reverse transcription) |
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Term
| Of the 4 polymerases of biosynthesis, which 2 are unique to viruses? |
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Definition
| Replicase and Reverse transcriptase |
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Term
| How are viral genomes more efficient than other genomes? (3 ways) |
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Definition
| Viral genomes can have overlapping reading frames, polycistronic mRNA can encode several proteins, and viral proteins are often translated as one large polypeptide and then cleaved |
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Term
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Definition
| Use DNA and RNA polymerase, and can use either host enzymes in the nucleus or use their own enzymes in the cytoplasm |
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Term
| Why do some DNA viruses replicate in the cytoplasm instead of the nucleus? |
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Definition
| They do not have to rely on the host's cell cycle. |
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Term
| What do proviruses do to a host cell's cell division? |
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Definition
| Increased or unregulated cell division |
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Term
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Definition
| Genes on a provirus that increase cell division and cause host tumor formation |
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Term
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Definition
| Uses replicase to go from +RNA -> -RNA -> +RNA, often happens in the cytoplasm |
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Term
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Definition
| mRNA, can be directly translated |
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Term
| -RNA & dsRNA viruses & what they have prepackaged |
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Definition
| Uses replicase to go from -RNA -> +RNA -> -RNA, often happens in the cytoplasm. Host ribosome cannot synthesize -RNA, so replicase protein is prepackaged |
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Term
| Reverse transcribing viruses |
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Definition
| Uses reverse transcriptase to go from RNA -> DNA and RNA polymerase to go from DNA -> RNA, DNA copy integrates into host genome, and provirus is created |
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Term
| Antigenic Drift vs. Antigenic Shift |
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Definition
Antigenic Drift~ slow, small changes in the virus. Mistakes during replication cause mutations and new strains. Replicase and reverse transcriptase are more error-prone
Antigenic Shift~ a large, rapid change. Recombination and reassortment. New strains or subtypes are very foreign to immune system |
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Term
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Definition
| 2 viruses chare a cell and create a subtype |
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