Microbiology: Microbial Genetics Flashcards
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Read the first 7 Microbiology: Microbial Genetics flashcards as text
Which of the following best describes the role of sigma factor in bacterial transcription?
Answer: It allows RNA polymerase to recognize and bind to specific promoter sequences
Sigma factor confers promoter specificity to the RNA polymerase holoenzyme, enabling it to recognize and bind the −10 and −35 consensus promoter sequences.
Insertion sequences (IS elements) are the simplest transposable elements in bacteria. What enzyme do they encode that is essential for their transposition?
Answer: Transposase
IS elements encode transposase, which catalyzes the cut-and-paste mechanism of DNA transposition by recognizing terminal inverted repeats and mediating strand cleavage and rejoining.
R plasmids (resistance plasmids) are clinically significant because they:
Answer: Can carry multiple antibiotic resistance genes and be transferred by conjugation
R plasmids often carry resistance genes for multiple antibiotics and can be conjugatively transferred between bacteria, rapidly spreading multidrug resistance in clinical settings.
In eukaryotic-like archaea, which feature of DNA replication differs most from the typical bacterial model?
Answer: Archaea can have multiple origins of replication like eukaryotes
Some archaea possess multiple origins of replication, a feature shared with eukaryotes but absent in most bacteria, which have a single origin (oriC).
A researcher finds that a mutant strain of E. coli has a mutation in the rpoB gene. Which cellular process is most directly affected?
Answer: Transcription
rpoB encodes the beta subunit of RNA polymerase; mutations in rpoB alter the enzyme's active site, which is the target of rifampin and affects transcription directly.
What is the significance of palindromic sequences in molecular genetics?
Answer: They are recognized and cleaved by restriction endonucleases
Most type II restriction endonucleases recognize specific palindromic sequences (reading the same on both strands 5'→3') and cut at or near these sites, making them essential tools in molecular cloning.
Quorum sensing in bacteria regulates gene expression based on:
Answer: Population density detected through signaling molecules
Quorum sensing uses small diffusible signaling molecules (autoinducers) that accumulate with cell density, triggering coordinated gene expression changes when a threshold concentration is reached.