Gene expression (THe deev) Flashcards
What is a multistep process that ultimately results in the production of a functional gene product (either RNA or protein)
Gene expression
True/False: We all started by one single cell
True
What are involved in basic cellular functions that are required regardless of cell type or environmental cues. are constitutively expressed and not regulated
Housekeeping genes
What are required only in certain cell types and/or only under certain conditions. Various control mechanisms which determine if and when the genes will be expressed.
Regulated genes
What genes are only required under certain conditions?
e.g. Betactin(sp?), part of the cytoskeleton
Regulated genes
What are the two classifications of genes?
Housekeeping genes and regulated genes
True/False: Prokaryotic cells have nucleus and mitochondria.
False they don’t have nucleus or mitochondria
Pro- NO
Eu- DO
Is mRNA ready to be translated immediately after transcription?
Yes, in prokaryotic genome whatever is encoded in the mRNA it is ready to be translated into proteins via ribosomes.
Transcription happens in _______.
Nucleus
Translation happens in _______ via _______.
Cytosol via ribosomes
Is RNA ready to be translated into proteins immediately after transcription?
No, There is post-transcriptional, and post-translational control with eukaryotes.
After proteins come out of translation are proteins ready to go do their job?
No, they need to be modified or degraded usually in Golgi apparatus via post-translational modification.
What is another role of control…“around genetics”
Epigenetics
Prokaryotic gene expression involves two regulatory molecules, what are they and what do they do?
Repressors- suppress the transcription of a gene
Activators- increase the transcription of a gene
What does the operon contain?
Control region and structural genes
What is the goal of any organism?
conserve energy,
“no organism wants to make enzymes that are not useful for anything”
What are two types of operons?
Repressible- transcription is usually ON but can be inhibited (repressed)
Inducible- transcription is usually OFF but can be stimulated (induced)
What is the inducible operon that we talked about?
Lactose operon (Lac Operon)
What is the prefered carbon source for E. coli?
Glucose, but has capability to use other sugars like lactose (only if it is necessary)
With Lac Operon if only glucose is present, is the Lac Operon on or off?
OFF
What is encoded by lacl gene, always present and bound to the operator, blocks RNA polymerase
Repressor protein is ALWAYS expressed
When glucose is sufficient, what happens to the Lac Operon?
Lac Operon is off
When only lactose is present, (no glucose) what happens to the Lac Operon?
Lac Operon is on
Glucose inhibits _____ ________, so there is no cAMP, cannot form CAP/cAMP complex , cannot initiate transcription
Adenylyl cyclase
If both glucose and lactose are present what happens to the Lac Operon?
Lac Operon is off
What are the 5 different levels of gene expression in Eukaryotes?
(TPTPE) Transcriptional Posttranscriptional Translational Post-translational Epigenetics
Why do you need more levels of regulation?
We are more complex as eukaryotes
What is the only similar level of control between eukaryotic DNA and Prokaryotic DNA?
Transcriptional control
Why is transcriptional control just a little different between Eukaryotes and Prokaryotes?
EUK- usually one gene encodes for one protein
PROK- ???
Influence expression of genes only on the same chromosome… only controls expression of genes that are downstream.
Cis-acting
Where does transcriptional control take place?
Usually embedded in noncoding region of the genome
Proteins are also called _______ regulators (transcription factors that interact with regulatory molecules).
Trans-acting
Binding of trans-acting regulators (TF) to DNA is achieved by one of the following 3 things:
ZInc Finger
leucine zipper
helix-turn-helix in the protein
What are DNA sequences that increase the rate of initiation of transcription.
Enhancers
True/False: Enhancers are typically on different chromosomes.
False: typically on same chromosome
What is the role of transcription factors?
DNA binding domain
Activation domain- stabilize formation of initiation complex recruit chromatin modifying proteins (i.e. histone acetylase)
_______ is a _______ hormone that diffuses into hepatocytes to regulate PEPCK gene expression.
Cortisol, steroid
True/False: Over 60% of ~25,000 genes in humans undergo alternative splicing.
True
What is an actin filament-binding protein, which undergoes tissue specific alternative splicing to produce multiple isoforms of the protein?
Tropomyosin
Apo B mRNA is made in the ______ and __________
liver and small intestine
Additional posttranscriptional modification in which base in mRNA is altered.
mRNA editing (e.g. Apo B mRNA)
The C residue in the CAA codon for glutamine is deaminated to U changing the sense codon to a ________ or _______.
nonsense or stop codon
What is a mechanism of reducing gene expression by repressing translation or increasing degradation of specific mRNAs… (widely used in research and has a lot of potential)
RNA interference (RNAi)
Neovascular AMD and VEGF lead to excess _____ ____ behind the retina. First clinical trial of RNAi for this helping macular degeneration.
blood vessels
RNAi is mediated by very short RNA (~20-22bp) called ______.
microRNA (miRNA)
miRNA acts as a _____ strand to target specific mRNAs that contain complementary sequence.
guide strand
What are siRNAs?
double stranded short interfering RNAs (siRNAs) introduced into a cell to trigger RNA interference.
What are mobile segments of DNA that move in a random manner from one site to another on the same or a different chromosome?
Transposons
What are regions in DNA that are rich in CG that are prone to modifications.
CpG islands
Phosphorylation of ___ inhibits GDP-GTP exchange and so inhibits translation at the initiation step.
elF-2
When elF-2 is phosphorylated by kinases what happens?
Translation is blocked
When elF-2 is not phosphorylated by kinases what happens?
Translation occurs
What are the 4 modifications of polypeptide chain?
Trimming
Covalent attachments
Protein folding by chaperones
Protein degredation by ubiquitination
Protein degredation happens by?
Ubiquitination
Protein folding is directed by what?
Chaperones
_______ is loosely packed and is accessible for transcription.
Euchromatin
_______ is tightly packed and is inaccessible by transcription.
Heterochromatin
