Final Exam : Exam 5 pt 2 Flashcards
Why is it not enough to control regulation of sugars individually
because the sugars often have a preferred substrate
Global regulatory mechanisms
-complex control system that regulates expression of cellular processes in microorganisms
-one event that triggers all proteins
best sugar
glucose
global regulatory mechanisms also called
catabolite repression
Catabolite repression
- mechanism that controls sugar usage
-helps us use glucose above all else
Catabolite repression is an example of
-positive of control of transcription
-activator protein
activator protein of catabolite repression
Cyclic AMP receptor protein
Cyclic AMP receptor protein
-common regulatory nucleotide
-also called cyclic GMP, di-GMP, and guanosine tetraphosphate
effector protein
cyclic AMP, tied to glucose
Cyclic AMP when glucose is present:
-Low cyclic AMP
-glucose inhibits adenylate cyclase (inhibit cAMP production)
-glucose causes the transport of remaining cAMP out of cell
-no RNA polymerase brought in bc no binding to activator
**seen before Lac operon
Cyclic AMP when glucose is abscent
-High cyclic AMP
-cAMP acts as inducer and draws in RNA polymerase
Glucose and lactose present
-no lactose utilization enzymes
-only glucose enzymes
No glucose but lactose is present
-no inhibition of adenylate cyclase
-lactose utilization genes will be made
if neither lactose or glucose present
repressor will be sitting on the operator
diauxic growth
-more exponential growth seen with glucose
-lag phase
-then less exponential growth w lactose
lag phase
when glucose runs out and have to wait for lactose to be brought in
two compartment regulatory system
links events occurring outside the cell to the regulation of gene expression inside the cell
two players in two compartment regulatory systems
-sensor kinase proteins
-response regulator proteins
sensor kinase proteins
-inside cell membrane (integral protein)
-autophosphorylation upon recognition of environmental cue
kinase
-phosphorylate proteins
-typically phosphorylate themselves (autophosphorylation)
categories of kinases
-serine-threonine
-tyrosine
-histidine
what residue doe phosphorylation occur at in sensor protein kinases
histidine residue
response regulator protein
-Cytoplasmic
-DNA binding protein
-effector is passing of phosphorylation
how do you reset system
feedback loop and phosphotase
phosphatase
removing phosphate from response regulator at a constant rate
mutations
-inherited change in the nucleotide base sequence of the genome
-relatively rare bc of proofreading mechanisms
-driving force of evolution
how often is there a mutation
every 108-109 base pairs
what do we have to fix mutations
repair mechanisms
why do we see more in prokaryotes than eukaryotes
-no backup copies of genes: haploid
-replicate very fast
mutant strain
-bacteria carrying mutation strain
-genotype will differ, phenotype may not differ
point mutations
when one base pair is substituted for another
silent mutation
-different sequence but allows for same amino acid to be coded for
-occur in wobble site
nonsense mutation
mutation allows a stop codon to be placed there causing for a incomplete protein
missense
-add in a different amino acid
-different amino acid than before
frameshift mutations
-when base pairs are inserted or deleted
-alters the reading frame
reverse mutations
when an earlier mutation is reversed by a second mutations
two types of reverse mutations
- same-site (true) reversion
- second-site reversion
same site reversion
converts the mutant nucleotide sequence back to original sequence
second site reversion
a second mutation occur at a different site in the DNA and causes the first mutation to be restored
second mutation found in
same gene or another gene
spontaneous mutation
-random change in DNA arising from errors in replication
-intrinsic
-quite slow (10-6 - 10-8)
induced mutations
-exposure to mutagens (physically or chemically) that interact with DNA in a disruptive manner
base analogs
-compounds that look similar to base used in DNA but have an extra group that attaches that modifies and causes a stable mutation
-point mutations
-need to be actively growing bc it cant be incorporated into dormant cell
DNA modifying agents
-mutagens that change the baes structure and therefor alter its base pairing
-addition of a group that attaches to a base that’s already there
Intercalating agents
-planar molecules that insert themselves between the stacked bases of the helix to induce single nucleotide pair insertions and deletions
-frameshift mutation
-disrupts DNA polymerase
non-ionizing Radiation
-excites an atom to a higher energy state
-UV radiation (260nm)
-not as penetrating a ionizing
-absorbed by DNA and targets pyrimidines bases forming pyrimidine dimers
ionizing radiation
-radiation ejects orbital electrons from an atom and causes ions to form
-gamma rays (most)
-X rays
-cathode rays (least)
why must we have repair mechanisms
-because mutations can alter nucleotide sequences, they must be able to repair any lethal changes
nucelotide excision repair
-UvrABC enzyme detects issue and cleaves out section
-fills in with DNA poly I
-DNA ligase makes final connection
base excision repair
-DNA glycosylase removes just the base yielding an apurinic/apyrimidinic site (AP site)
AP endonucleases
-recognizes AP site, and nicks the DNA backbone
-DNA poly I put in correct nucleotide
-DNA ligase makes final connection
Direct repair
photoactivation
photoactivation
-light activated repair
-photolyase
-used for dimers
SOS repair system
-seen in extreme conditions and a lot of errors
-Rec A protein
-Lex A protein
-Sfi A
-Translesion DNA synthesis genes
Rec A protein
-activated due to stalls in replication
-triggers Lex A repressor to cleave itself to initiate gene transcription
-increases transcription of genes for excision repair
-produces Sfi A
Lex a repressor
found in operator region of SOS gene
Sfi A
blocks cell division
Translesion DNA synthesis
breakage and no longer have a template, use DNA poly IV and V which have no proofreading capabilities
selection mutant isolation
-confers to an advantage for the organism
-antibiotic resistance
screening mutant isolation
-examining large numbers of colonies for certain types of mutations
-non-selectable
-nutrient deficiencies
Replica plating
used ti detect auxotrophic mutants
A lysine auxotroph only grows on
lysine supplemented media
