Week 8 & 9 Flashcards
Explain the importance of gene regulation (control of gene expression)
Gene regulation is the process of controlling which in a cell’s DNA are expressed.
It is important because it acts as both an on/off switch to control when proteins are made and also a volume control that increases or decreases the amount of proteins made. It allows a cell to respond to its changing environment.
Why would we not produce all proteins continuously?
It would require a lot of energy, therefore it would waste energy and ressources. Not producing all proteins continuously allows to accord the protein a specific function.
What is an Operon?
An operon is a set of genes transcribed under the control of an operator gene. It contains a promoter (where transcription starts), an operator (a genetic sequence which allows proteins responsible for transcription to attach to the DNA sequence) and a gene sequence (the information on how to build proteins).
*The RNA polymerase III will sit on the promoter so that it can transcribe the DNA.
What is a repressor active and inactive?
A repressor is a protein that works by binding to the gene’s promoter region, therefore it would prevent the production of mRNA.
When the repressor is active is when lactose is absent, so the operon (set of genes transcribed under the control of an operator gene) binding to the operator would switch off.
When the repressor is inactive is when the lactose is present so it will prevent the operon to bind to the operator.
When should genes of the lac operon be expressed?
When the bacteria has lactose.
Explain differences between inducible (IE. Lac Operon) vs. repressible operons (IE. Trp Operon)
The main difference is that the inducible operons are turned off under normal conditions while the repressible operons are turned on under normal conditions.
What is the importance of regulation in multicellular organisms?
Gene regulation allows cells to react quickly to changes in their environment. The fact that we regulate carefully the cell growth in a multicellular organism it has less chances of growing out of control or form masses of cells.
Explain how epigenetic contribute to gene regulation in eukaryotes
Epigenetic can be on and off depending on the environment.
It is possible of doing gene regulation (controlling gene expression since the transcription and translation are not in the same compartments)
They have the control access to the chromosomal region to allow genes to be turned on or off.
Epigenetic may be passed on to offspring. They may be involved in cancer, auto-immune diseases, etc.
What are the proteins (transcription factors) that interact with the DNA sequences (patterns) to regulate transcription (in Eukaryotes)?
Activator protein binds to the enhancer sequence to facilitate transcription.
Repressor protein binds to silencer sequence to prevent transcription.
Therefore, if we want to transcribe there is an activator protein that will bind with the enhancer sequence.
What is the role of a histone protein?
Histones are associated with DNA in the nucleus and help condense it into chromatin
What is Acetylation and Methylation?
Acetylation is regions with high transcriptional activity that are loosely packed. Acetylation takes part in the Euchromatin.
Methylation is regions with low or no transcriptional activity that are densely packed (no mRNA, no translation). Methylation takes part in the heterochromatin, which is usually found at the centromere (which is generally gene poor).
How are genes switched on vs off
On:
The gene is switched on when the chromatin is active. Therefore, the histones will be acetylated (they will be loosely packed).
(Euchromatide)
Off:
The gene will be switched off when the chromatin is silent. Therefore, the histones will be deacetylated, so no transcription will be formed (transcription impeded)
(Heterochromatide)
Describe the roles of transcription factors (activator, repressor) and DNA control regions (enhancer, silencer, promoter)
Activator increases the rate of transcription.
Repressor turns off the expression of one or more gene.
Enhancer is a regulatory DNA sequence that promotes transcription.
Silencer is a DNA sequence capable of binding transcription regulation factors, called repressor. They prevent genes from being expressed as proteins.
Promoter is a DNA sequence that define where transcription of a gene by RNA polymerase begin.
What are other type of regulations?
Post-Transcription: preventing passage of messenger RNA out of nucleus and into the cytoplasm
Post-translation: Modifications to protein structure affect may facilitate/prevent degradation.
Explain the molecular changes that allows vs prevents transcription
When the transcriptional repressor binds to the promoter, there will be no transcription since the repressor will block the way.
