Viruses & Bacteriophages
What kinds of capsid does the cow pox virus have?
Asymmetrical/irregular
What are the components of an operon?
Promoter, operator, & structural genes
If there is a mutation in a codon sequence, but both combinations produce Tyrosine, what kind of mutation is this?
Silent mutation
What is a missense mutation?
A nucleotide change that results in the coding for a different amino acid.
What are the basic steps of the viral life cycle?
1. Absorption - Attachment of virus to host cell
2. Penetration - Entry of virus
3. Uncoating - Capsid removed from genome
4. Genome replication & protein synthesis
5. Virion assembly - new viruses are put together
6. Release - new viruses leave host cell
What kind of viruses do not have envelopes?
What do anti-sigma factors do?
Bind to sigma factors and prevent their binding to RNA polymerase.
Where does the charged tRNA enter the ribosome?
The A site
A gene sequence is altered from AGCTCG to AGCGTCG. What kind of mutation is this?
Frame shift/insertion
What kind of viral life cycle does the bacteriophage T4 use?
Virulent (also called lytic)
What is a prophage?
A viral genome that is inserted into the host DNA
What happens to the cAMP production and Lac operon expression when glucose and lactose levels are both high?
low cAMP, low Lac operon transcription
What is the function of the Shine Dalgarno sequence?
The ribosome binding site on mRNA.
In what situations would error-proof repair be used, vs error-prone repair?
Error-proof would be used for small changes, such as a single base mutation, whereas error-prone repair would be used for big changes, such as a break in the DNA strand.
What do viruses not rely on the host cell for?
Genome replication
A virus has an -ssRNA genome. What needs to happen before it can transcribe its genome to +mRNA?
Nothing, it can go straight to transcribing its genome to +mRNA.
What happens to rpoH mRNA when the cell's environment reaches at least 42°C?
The secondary structures preventing the rpoH mRNA from being translated are melted by the heat, so the rpoH protein can be produced. Then, it can bind to RNA Polymerase and promote the expression of the heat-shock response genes.
Why do RNA viruses induce more mutations than DNA viruses?
The RNA polymerase likely does not have a proofreading mechanism
What is a Restriction-Modification system and what does it do (as in relation to viruses/bacteriophages)?
Prevents bacteriophage infection by cutting the bacteriophage DNA at specific points.
What are the early genes transcribed by the T4 phage?
Genes for nucleases, replication proteins, sigma factors, RNA polymerase-modifying proteins
How can the number of virions released after infection from a bacteriophage be determined?
Counting the number of plaques formed
How do bacterial cells regulate the production of a protein? (Hint: 3 ways)
Post-translational, regulation of gene transcription, regulation of mRNA translation
Where is the growing polypeptide chain during translation?
Going between the tRNA in the P site and A site
What is the purpose of RecA in error-prone DNA repair?
Cleaves LexA to allow for the transcription of the SOS response system proteins.
What are the protein synthesis strategies of influenza, HIV, and Hep C? (points for 2/3 correct)
Influenza: Segmented genome strategy (genome is not all together)
HIV: Splicing strategy (separate mRNAs are made and then cut up)
Hep C: Polyprotein strategy (really big proteins are made, then split into proteins that can be used)