Virology Quiz #1 Part 2 Flashcards
Which direction do polymerase read the template strand? Which direction is the anti-parallel strand synthesized?
Read: 3’-5’
Synthesize: 5’-3’
Which direction do ribosomes read mRNA template? Which direction do they synthesize the polypeptide?
- read: 5’-3’
- synthesize: N-C
Why do viruses package their own replicative enzymes in their capsids?
- Some species of viruses replicate their genomes in the cytoplasm of the cell (can’t use DNA/RNA pol in the nucleus)
- For RNA viruses: cell’s RNA pol does not read an RNA template (it reads DNA)
How do DNA viruses replicate/express genome in the nucleus? How do they replicate in the cytoplasm?
Nucleus: uses cell’s DNA/RNA pol
Cytoplasm: genome encodes DNA/RNA pol, or capsid contains pre-made DNA/RNA pol
How do RNA viruses replicate in the nucleus? How do they replicate in the cytoplasm?
Nucleus: encodes RNA pol, may contain pre-made RNA pol
Cytoplasm: encodes RNA pol, may contain pre-made RNA pol depending if (+) or (-) sense (+sense RNA virus can synthesize it after infecting the cell, - sense RNA viruses must have some packaged within capsid)
What does reverse transcriptase do?
Reads RNA and synthesizes DNA to make a DNA-RNA hybrid molecule
How are viruses assembled from their parts?
- components have “affinity” for each other, and parts are assembled into pre-vision structures, then virus is inserted
How do viruses egress?
Naked: cell lysis, dies, all progeny egress at once
Enveloped: virus buds out, continued virus production
Why are capsids made using subunit construction?
- Genetic economy: single protein cannot cover; less genetic material is required if the protein unit is used as a repeated unit
- Economy: misfolding a protein is very common
How are virus genomes selected from all of the nucleus acid that might be present in a cell?
Specific nucleus acid-protein interactions (ex. Spliceosomes removing introns from RNA, sites where DNA pol bind to replicate the chromosome)
