LG 6.15 - Pathogen Adaptation Flashcards
What is the area that bacterial genome replication begins? What direction? Conservative?
- OriC
- Bidirectional
- Semi-conservative
How do bacteria speed up replication?
- Multiple replication forks in log-phase growth.
- Open up multiple forks.
What relieves the overwinding of DNA during replication? What is one tactic of antibiotics targeting bacteria regarding this?
- DNA gyrase, type 2 topoisomerase.
- Inhibitors of bacterial DNA synthesis may target these topoisomerases.
Where does RNA polymerase bind on bacterial DNA? How does it identify this region?
- Binds TATAA boxes (promoter region).
- It uses sigma factors to identify this region.
Regarding how many proteins it can make, what is different between eukaryotic mRNA and prokaryotic?
- Prokaryotic mRNAs are polycistronic, can code for multiple proteins on one strand of mRNA.
- eukaryotes are monocistronic
What is the initiator tRNA in translation? What codon does it match up with?
- fMET - not the initiator in eukaryotes
- AUG
How large are the ribosomes compared to eukaryotes?
- 30s subunit, and 50s subunit, making 70s subunit.
Which subunit on the ribosome does what? What are the two sites on the ribosome?
- 50s catalyzes peptide bond formation.
- 30s decodes the mRNA
- “Peptidyl” (P )site contains the growing peptide chain.
- “Aminoacyl” (A) site accepts the incoming tRNAs
Are transcription and translation happening at two separate times?
- They are coupled
What is a general cause of mutation in bacteria during DNA replication, how is this fixed? What happens if not fixed?
- Most mutations are spontaneous.
- most are Repaired via proofreading (but 3 additional methods too. see other cards).
- mutations can be detrimental. can be advantageous!
What is DNA mismatch repair?
- method of bacterial DNA repair. occurs via methylation of parental strand, newly synthesized DNA strand with error is replaced
What type of physical agents can also damage bacterial DNA?
- Heat
- Ultraviolet light
- Ionizing radiation
What type of chemical agents can damage DNA?
- Nucleotide-base analogues
- Frameshift mutagens
- DNA-reactive chemicals
What is DNA excision repair
- method of bacterial DNA repair.
- Damaged is cut out and polymerase comes back and fills in proper sequence.
- nick is repaired by DNA ligase
What is DNA recombination repair?
- method of bacterial DNA repair: polymerase will bypass a damaged parent strand region - leaving a gap in new strand - and recombine with another chromosome later to bypass the damaged region.
- gap replaced by another strand
What is the difference between a neutral and radical substitution/mutation?
- Neutral: conservative substitution.
- wrong amino acid translated results in mutated protein - same shape (i.e. same function) as original.
- Radical
- Mutated protein is different shape (i.e., different function) than original.
Regarding mutations in bacteria how often do they occur? Are they immediately evident? If it is an advantageous mutation what will occur because of the short generation time?
- Mutations occur at low frequency, but large population size.
- Haploid so mutations are immediately evident.
- Short generation times so if a mutation is advantageous it will dominate.
What are the two types of recombination in bacteria, and how do they differ?
- This is a method of chromosome shuffling WITHIN the cell.
- Homologous recombination: requires large segments of sequence identity.
- Site-specific: requires recognition of unique DNA sequences and specific enzymes.
What is a transposon?
- This is a method of chromosome shuffling WITHIN the cell.
- “Jumping genes”
- Segments of DNA that may jump within or between chromosomes or plasmids.
What elements must transposons have?
- Inverted repeats
- Gene for transposase: enzyme that allows for jumping.
What are the two types of transposons?
- Conservative: transposon is transferred to new plasmid, leaving last plasmid without transposon.
- Replicative: transposon creates a duplicate in the target DNA, original keeps genes. Needs transposase and resolvase genes
What is bacterial conjugation, how does it occur?
- Sharing of genetic information.
- F plasmid in F+ cell contains genes for sex pilus and conjugation tube for transferring the plasmids to an F- cell.
What is the mechanism of plasmid transfer in conjugation?
- Single nick in plasmid and transfer the plasmid as single strand of DNA.
- Plasmid could remain by itself or be integrated into the DNA.
How do temperate bacteriophages work?
- They integrate their DNA into host DNA and wait until they want to reproduce and they go from lysogenic cycle to lytic cycle.
