Microbiology Test 1
external signals for sporulation
desiccation, starvation, cell density
-->sigmaF is released -->activates sigmaE -->signal from mother cell triggers sigmaG in endospore and sigmaK in mother
endospore formation is regulated by
Sequences at the end of the gene trigger release of the polymerase and the completed RNA molecule
The sequential addition of ribonucleotide from nucleoside triphosphate to the 3’OH end of the growing chain
Bind of the RNAP to the beginning of the gene, followed by opening the DNA helix and start of RNA synthesis
Transcription (DNA to RNA) is carried out by RNA polymerase.
• RNA polymerase uses DNA as template.
• RNA precursors are ATP, GTP, CTP, and UTP.
• chain growth 5′ to 3′, just as in DNA replication
- only one strand transcribed
- no priming needed
Which statement is TRUE regarding protein synthesis?
The 23S rRNA catalyzes peptide bond formation in the growing polypeptide chain.
Transport to Periplasm via TAT system
used for folded proteins
- Signal sequence RRXFXK • TAT System
- Powered by Proton Motive Force (PMF)
Transport of synthesized protein to periplasm
protein wraps around SecB--> goes over to SecA and SecYEG(embedded in membrane) -->protein is pushed through SecYEG with help from SecA and ATP and goes into periplasm -->LepB cleaves the signal sequence -->protein is folded in periplasm
Signal Recognition Particle
Transport to membrane: Protein is synthesized & localized
Protein is unfolded
clusters of ribosome bound to an mRNA
- Stop codon (UAA, UGA, UAG)
- release factor (either RF 1 or RF 2) enters A site, no tRNA for stop codons
- Peptidyltransferase is activated and releases the completed protein from tRNA in the P site
- Ribosome recycling factor (RRF) & EF-G undocks 50S from 30S
- IF3 removes uncharged tRNA & mRNA
- EF-Tu-GTP binds tRNA, binds A site, GTP hydrolysis
- Peptidyltranferase makes peptide bond
- EF-G-GTP, hydrolysis of GTP, tRNA moves to P site
-E.coli- IF1, IF2 & IF3
-M. jannaschii- 6 IF proteins
An operon is a useful genetic element, because it
allows coordinated expression of multiple related genes in prokaryotes.
Transfer RNA (tRNA) molecules
function to transfer the correct amino acids to the ribosome during translation.
Initiation is at any Shine– Dalgarno sequence; the mRNA can therefore be a polycistronic mRNA that codes for several polypeptides.
What is an operon and why is it beneficial to link expression of certain genes?
An operon is a cluster of genes that are under the control of a single promoter and are therefore cotranscribed as a single, polycistronic mRNA molecule. This arrangement allows related genes to be expressed in a coordinated fashion
structure of an ORF
Ribosomal binding site-Start codon-coding sequence-stop codon
Global regulatory systems include all of the following EXCEPT
amino acid synthesis
heat shock response
amino acid synthesis
Attenuation is a type of regulation that can control
transcriptional activity exclusively
The function of a kinase is
Which of the following do NOT bind to the promoter sequence during regulation?
None of these bind directly to the promoter sequence
none of these
The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occu
negative / inducer
recombination-associated chi sites accumulate in the _____ strand
Gene strand bias results in more genes in the _____ strand
The Par system is necessary for
distribution of genetic material in replicating Caulobacter.
Promotes growth of stalk, cell elongation and division
- GcrA levels rise and promotes elongation phase of chromosome replication, cell division & growth of the the stalk on immobile daughter cell
- GcrA levels fall, and high levels of CtrA reappear in the daughter cell
Transcriptional regulator for flagellar synthesis; represses GcrA expression & DNA replication
- CtrA is activated by phosphorylation • CtrA~P activates genes need for flagella & represses synthesis of GcrA & • CtrA~P inhibits the initiation of DNA replication by binding the origin.
- CtrA gets degraded by a specific protease resulting in increasing DnaA levels
- Absence of CtrA allows for DNA replication to initiate • DnaA is then also degraded by a protease
- Aquatic bacterium with differential life styles – Swarmer – Stalked/attached
- Good to study cell cycle in
The curved-rod shape typical of Caulobacter is due to the proteins ____ and ______
crescentin and MreB
- Can phenotype change without a change in genotype?
- Phenotypic changes often occur without a genotypic change when an organism is placed in a different environment. This could be due either to changes in gene expression or abiotic (physical or chemical) factors that alter a gene product.
- Does the phenotype of an organisms change when the genotype changes?
- Phenotypic changes do not always accompany genotypic changes. Genotypic changes that do not alter the phenotype could be due to point mutations that do not result in changes to the primary structure (amino acid sequence) of a protein (i.e., silent mutations)
- The observable characteristics of an organism based on its genetic composition.
- The complete genetic makeup of an organism. Its precise determination would require genomic sequencing
Replication errors --> correction and repair
-Proofreading (make sure A & T together and C & G together)
-Thiamine dimer (detects damaged bases -->cuts nucleotides-->replaces nucleotides that were cut-->nucleotide linkage)
septation is directed by ____
origin of replication
After DNA helices has moved approx. _____ bases, another ___ primer is synthesized on each lagging strand
G & C have ___ hydrogen bonds
A & T have ___ hydrogen bonds
proofreading begins at time of _____ insertion
binds terminus and blocks progress of the replication fork
seals nicks in DNA
DNA polymerase I
excises RNA primer and fills in gaps
Dimerization subunit (Tau)
holds together the 2 core enzymes for the leading and lagging strands
loads Poly III onto sliding clamp
an enzymes ability to catalyze consecutive reactions w/o releasing its substrate
sliding clamp (beta clamp)
holds Poly III on DNA
involved in processivity; processivity factor for DNA polymerase
binds DNA polymerase III and prevents dislocation
3' to 5'
DNA polymerase III
main polymerizing enzyme; the main replication polymerase
subunit for proofreading (dnaQ)
priming; primes new strands of DNA
RNA primer synthesis
rifampin resistant RNA polymerase
single-strand binding protein
cover and protect the unreplicated single strand
unwinds double helix at replication fork
helicase loader; loads helicase at origin
open the DNA helicase protein ring and place the ring around the single-stranded DNA at the origin. Loading of the DNA helicase leads to the release of the helicase loader
origin binding protein; binds oriC
binds origin of replication to open double helix
binding of dnaA leads to the strand separation at the 13-mer repeats
replaces supercoils ahead of replisome
one helical turn has ____ base pairs
thymine and cytosine
Adenine and Guanine
required for correct placement of division site