LECTURE 6 - Gene Regulation Flashcards
cells contain the ____ ____ for the _____ of different products
- genetic capacity
- synthesis
WHAT mechanism is present for the control of gene expression
regulatory mechanism
GENE REGULATION
- controls the (3)?
- occurs in what type of organisms?
- helps conserve ____ by producing ______ only when _____
+ 4 importances and example
- timing, location, and amount of gene expression (which, when, how much)
- prokaryotic and eukaryotic organisms
- energy
- proteins
- when needed
- Cellular Differentiation
(allows stem cells to differentiate) - Metabolic Efficiency (prevents unnecessary expenditure)
- Response to Environment (enables organisms to adapt to changes)
- Disease Prevention (abnormal regulation can lead to cancer - over-multiplication of cells)
EUKARYOTES vs PROKARYOTES in gene regulation in terms of:
- Organization
- Transcription and Translation
- RNA processing
- Regulation
PROKARYOTES:
- Genes often grouped into operons
- Occur simultaneously in the cytoplasm
- NONE, mRNA is directly translated after transcription.
- Primarily at the transcriptional level using repressors and activators.
EUKARYOTES:
- Genes are individually regulated
- Transcription in nucleus; translation in cytoplasm
- mRNA undergoes splicing (removal of introns), capping, and polyadenylation before translation.
- Multi-level: ex. posttranscriptional and posttranslational.
in ____ organisms, gene regulation occurs at least at _____ levels
+ what are these levels?
- most
- 2
- transcriptional level
- post-transcriptional level
the 2 regulatory levels operate with some _______ in _____ and ______
- modification
- prokaryotes
- eukaryotes
IN EUKARYOTES,
when can CONTROL be achieved (2)?
CONTROL is achieved at the stage wherein _____ is ____ from the nucleus
and is also achieved ____ the _____ of the polypeptide chain
- when the mRNA is released from the nucleus
- after the synthesis of the polypeptide chain
WHAT is the primary target of controlling mechanisms?
+ In (WHAT organisms) does this happen?
+ reason for this being the primary target?
TRANSCRIPTION
- prokaryotes and viruses
due to the different ways for enzymes to be synthesized
WHAT are the 2 types of enzymes that affect gene regulation in transcription?
- Constitutive Enzymes (housekeeping)
- mRNA for these enzymes are synthesized continuously REGARDLESS of environmental conditions - Inducible Enzymes** (adaptive)
- synthesis of mRNA for these enzymes increases in the presence of substrate (or occurs in specific conditions)
**normally present in small amounts but concentrations increase when substrates are present
RELATED GENES (specifically in ___)
- are generally ______?
- their GENE PRODUCTS / enzymes belong…?
- consists of a genetic unit called ____?
- prokaryotes
- clustered together
- belong to the same metabolic pathway
OPERON
OPERON
- a unit of _____ that is a ____ of ____-related ____?
- allows the _____ _____ of genes with _____ functions
- 2 types of operon systems? + definition
- DNA
- group
- functionally-related
- genes
- coordinated expression
- related
- Inducible
- system is naturally off
- wherein effector molecules induce weakly transcribed operons - Repressible
- system is naturally on
- wherein effector molecules repress the transcription of an operon
In E coli
- what type of inducible operon is present?
- what are its ^^ 4 adjacent parts?
- lactose or lac operon
- regulator gene (lacl)
- promoter site
- operator site
- 3 structural genes (z, y, and a)
In E coli, LAC OPERON
- what regulator protein is present?
- what type of regulator protein is it?
- other term?
- In ^^, all its subunits are ____
- each subunit in ^^ is a ___ that is coded by WHAT GENE?
- laci repressor (repressor protein)
- tetramer (protein with 4 subunits)
- identical
- polypeptide
- laci gene
REPRESSOR PROTEIN
- main function?
- makes the operon to be “____ ___” or “___”
- binds to operator during TRANSCRIPTION to block the movement of RNA polymerase from promoter to structural genes to hinder the synthesis process
- turned off or repressed
IF the lac operon is in repressed state, will there be ENTIRELY no transcription done?
no, there will still be a low concentration of proteins coded by the structural genes
LAC OPERON
- the 3 structural genes present here are involved in the _____ of ______ for ______ release
+ what enzymes do each of the structural genes code for?
+ function of these enzymes (2 ; 1 ; 1)
- metabolism
- lactose
- energy
- LacY
- β-galactoside permease
- a transmembrane transport protein that allows entry of β-galactosides (like lactose) from environment into the bacterial cell - LacZ
- β-galactosidase
- breaks down lactose (from environment) into glucose and galactose
- catalyzes conversion of lactose to allolactose - LacA
- β-galactoside transacetylase
- involved in other aspects of β-galactoside metabolism
ALLOLACTOSE
- an isomer of ___
- function?
- consequence of function ^^?
- lactose
- binds to the repressor (in the operon) and induces it to change conformations, thereby releasing the repressor protein and TURNING ON the operon
- transcription then proceeds at a high rate
LAC OPERON
- basic step-by-step process?
- β-galactoside permease lets outside lactose to enter bacterial cell
- β-galactosidase converts the lactose to glucose, galactose, and allolactose
- Allolactose is used to “turn on” the lac operon by affecting the repressor
- Transcription occurs at high rate until all the lactose molecules have been used up (wala nang pwede i convert to allolactose)
- Lac operon turns off again
In E coli
- what type of repressible operon is present?
- what are its ^^ 5 adjacent parts?
- tryptophan operon
- regulator gene (trpR)
- promoter site
- operator site
- attenuator site (trpL)
- 5 structural genes (trpE, trpD, trpC, trpB, trpA)
LAC OPERON VS TRYPTOPHAN OPERON
- type of operon system
- regulator gene
- location of regulator gene
- activity of regulator gene
LAC: inducible
- lacIgene
- located upstream near the lac operon
- active by itself (so lac repressor can automatically bind to lac operon)
TRP: repressible
- trpR gene
- located far away from trp operon
- initially inactive (so the trp repressor by itself cannot bind to the trp operon)
In E coli, TRP OPERON
- what regulator protein is present?
- other term?
- In ^^, all its subunits are ____
- each subunit in ^^ is a ___ that is coded by WHAT GENE?
- trp repressor
- dimer (2 subunits)
- identical
- polypeptide
- trpR gene
TRP REPRESSOR
- since it is initially inactive, what is its other name?
- what attaches to this protein to become active?
- for the trp operon, what will the attached protein be?
- aporepressor
to become active, a COREPRESSOR must attach with the aporepressor
- the corepressor is the tryptophan
TRP OPERON
- the 5 structural genes present here are involved in the _____ of ______ for cell metabolic processes like ______
+ what enzymes do each of the structural genes code for?
+ function of these enzymes
- biosynthesis
- tryptophan
- translation
- trpE + trp D (1st 2 steps)
- anthranilate synthetase - trpC (2nd 2 steps)
- indole-3-glycerol phosphate synthase - trpB + trpA (final step)
- trytophan synthethase
TRP OPERON
- basic step-by-step process?
- the 5 structural genes is continuously synthesized by the RNA polymerase into TRYPTOPHAN (since the trp repressor is inactive by itself)
- once the concentration of the tryptophan inside the cell becomes too high, a tryptophan molecule (that acts as a corepressor) binds to the aporepressor to activate the trp repressor
- turns off the trp operon
FUNCTIONS of OPERON COMPONENTS
- regulator gene
- promotor
- operator
- structural genes
- terminator
- codes for repressor protein that bind to operator to regulate operon activity
- binding site for rna polymerase to intiate transcription
- regulatory dna sequence located NEAR or WITHIN promoter
- actual genes within the operon that encode proteins
- signals end of transcription
DETERMINE WHAT WILL HAPPEN:
LAC OPERON:
1. No lactose
2. W/ lactose
TRP OPERON:
1. Low tryptophan
2. High tryptophan
- lacI repressor continues to bind -> no transcription
- allolactose is produced -> binds to repressor -> inactivates repressor -> transcription proceeds
- operon is active to synthesize more tryptophan
- acts as corepressor and binds to trpR repressor -> activates repressor -> no transcription
2 MAIN types of GENOMIC RESEARCH
- Structural (direct determination of complete DNA sequence)
- Functional (identify gene functions and interactions in relation with phenotype + the turning on and off of genes)
pre - MRNA processing
- what organisms is this done?
- STEPS (3)
- only in EUKARYOTES
- addition of 5’ cap
- 7-methyl guanosine
- protects mRNA from degradation
- assist in translation - splicing of introns by SPLICEOSOME
- introns: intervening DNA sequences between exons
- exons: gene sequences that code for amino acids - addition of poly A tail at 3’
- protects mRNA from degradation
- aids in transcription termination
- exports mRNA from nucleus to ribosome
SPECIAL TRANSFERS
- happens in viruses
- 2 types
- RNA replication
- Reverse Transcription (reverse transcriptase)
TRANSCRIPTIONAL CONTROL
- 2 types
- Negative Transcriptional Control
- needs REPRESSOR protein to turn off - Positive Transcriptional Control
- needs EXPRESSOR protein to turn on
