Gene Expression Flashcards
Encoding protein
Structural genes
Encoding products that interact with other sequences and affect the transcription and translation of these sequences
Regulatory genes
DNA sequences that are not transcribes but play a role in regulating other nucleotide sequences
Regulatory elements
Regulation of gene expression occur simultaneously in the cytoplasm
Prokaryotes
Gene expression is regulated primarily at …..
Transcriptional level
Gene regulation occurs at the epigenetic, transcriptional, post-transcriptional, translation and post-translational level
Eukaryotic
Continuously expressed under normal cellular conditions
Constitutive expression
Positive control
Stimulate gene expression
Negative control
Inhibit gene expression
Gene regulation is through…..
Chemical modification of chromatin/histone
During transcription, gene regulation occurs through…
Transcription, RNA processing and translation
Eukaryotic DNA is package as…
Chromatin
Proteins that carry out transcription cannot access the DNA due to..
Chromatin being coiled
Chromatin unravel to allow space for….
Transcriptional enzymes and proteins
During chromatin remodelling, the nucleosomes are….
Repositioned to expose different stretches of DNA
Remodelling can be due to chemical modification of ….
Histone tails
Individual amino acids can be modified by the addition/removal of
Methyl and acetyl
CpG is…
Addition of methyl group to cytosine in DNA
CpG sites are often …. and near the …..
Clustered
Promoter region
Methylation can …. over time or due to ….. response
Change
Environmental
Heavy methylated CpG
Inhibits transcription
Undermethylated CpG
Allows transcription
Changes to the manner in which DNA is packaged, causing changes in gene expression
Epigenetic effects
Th dosage of genes is twice as great in remains as it is in males
Genes on X chromosome
Level of expression of X-linked genes is…. in both sexes
Equal
Differential regulation is called…
Dosage compensation
Inactivation of one X chromosome in each female cell
X-inactivation
X-inactivation occurs at…
The time of implantation in the uterine wall
The Xist non-coding RNA binds with the…
X-inactivation centre (XIC)
Transcription of Xist contributes and the X-inactivation becomes coated with….
Xist RNA
As transcription continues, the entire chromosome becomes coated with …… and triggers …… therefore ……..
Xist RNA
Methylation
Transcription reduced
Regulatory transcription factors bind at…. and the general transcription factors bind at ….
Enhancer sequences
Promoter region
General transcription factors can recruit…
RNA Polymerase complex
Transcription only takes place when all the regulatory transcription factors are…
Present and working together
Some regulatory transcription factors bind to silencers and ….
Repress transcription factors
Gene with multiple silencers and enhancers dependent on combination of regulatory transcription factors
Combinatorial control
Adenosine——>
Deamination
Inosine
Cytosine ——>
Deamination
Uracil
Regulates by either binding to transcript and blocking translation, binding to transcript and causing degradation
Small Regulatory RNA
RNAs fold back on itself to form a …
Hairpin structure
Enzymes recognise mRNA and cleave the stems of hairpin leaving …
Small, double stranded fragments
How many strands incorporated into protein complex (RISC)?
One
What targets a region or mRNA?
RISC
Does small regulatory RNA inhibit or allow translation?
Inhibit
Degradation of RNA transcript caused by…
Target mRNA cleaved by RISC
Post-translational modification is important because…
Some proteins are dangerous
Translation machinery
5’ cap
Proteins bind
5’ UTR
Specific proteins bind
3’ UTR
Translation inhibited post-translational level by?
Poly(A)
Proteins are modified by the addition of one or more …… to side chains of amino acids.
A reversible addition of ….. to side chains
Marking proteins for ….. by addition of chemical groups
Sugar molecules
Phosphate groups
Enzymatic destruction
Activator protein binds to DNA for transcription to take place
When activator protein is not present or able to bind to DNA, transcription does not occur
Positive regulation in prokaryotes
A regulatory molecule binds DNA in order for transcription to be prevented
RNA polymerase cannot be recruited so no transcription
Negative regulation
Region of DNA that includes the coding sequence for multiple genes that get transcribed together into a single molecule of mRNA
Operon
Gene for B-galactosidase
Lactose —-> glucose and galactose
Lac Z
Gene for lactose permase
Transports lactose from external medium into cell
Lac Y
During regulation of the lac operon is the ….. which encodes for …..
Lacl gene
Repressor protein
Repressor binds with the operator, the RNA polymerase complex is not recruited and transcription does not take place
Absence of lactose
Acts as an inducer because it prevents binding of repressor protein
Lactose
Lactose causes ….. to be produced
Allolactose
Lacl mutants do not produce functional repressor therefore….
Lac Z and Lac Y are expressed in presence and absence of lactose
Two copies of operon are…
Wild
Mutation
CRP-cAMP complex is a …. regulator of the lac operon
Positive
CRP-cAMP is more sensitive to the ….. needs than ….
Nutritional
Lactose
cAMP levels are high
cAMP binds to CRP
CRP to DNA
Transcription activates
Absence of glucose
Lactose operon is induced when ….
Lactose is present
Lactose operon is not transcribed, even in present of cAMP-CRP
Lactose not present
cAMP levels are low
CAMP-CRP does not form
CRP does not bind to lactose operon
Presence of glucose
…… utilises glucose when both glucose and lactose are present
E.Coli
Occurs in normal cells in good condition
Virus uses cellular machinery of host to produce viral proteins
Host cell bursts
Lytic pathway
Takes place in cells in poor conditions
Bacteriophage DNA undergo a process of recombination at specific sites
Enlarged bacteriophage DNA in bacterial cell
Lysogenic pathway
Predominance of cro protein
Lytic
Predominance of cl protein
Lysogenic
In prokaryotic cells, activators and repressor ….. and ….. transcription rates
Increase
Decrease
Controls access to DNA sequences
Nucleosome spacing
Access to DNA is controlled by
Histone modification
RNA splicing removes ….
Introns
Untranslated regions maintain
RNA stability
Proteins can be recycled after being tagged with ….
Ubiquitin
Described as a disease of altered gene expression
Cancer
