(9) Regulating Gene Expresison Flashcards
(28 cards)
What is the core concept of gene regulation?
Each even that takes place in the expression of a gene is a potential control point for gene expression.
What is the most common chemical modification to DNA?
The addition of a methyl group to the base cytosine.
(T/F) Methylation of a CpG island can change over time.
True
Where does DNA methylation often occur?
In cytosine bases that are adjacent to guanosine bases on a DNA strand.
Where are CpG sites often clustered? What is the name of these clusters?
Near the promoter of the gene.
CpG islands
When chromatin is coiled (heterochromatin), can the proteins that carry out transcription access the DNA?
No
Through what mechanism are proteins able to access DNA when chromatin is coiled?
Chromatin remodeling unravels to allows space for transcription (enzymes and proteins doing their job)
What are major targets of chemical modification?
Lysine and arginine amino acids (positively charged)
Methylation and acetylation of lysine and arginine amino acids often increases expression, but may silence expression also. What does this difference depend on?
The amino acid position and degree of chemical change
Why does chromatin remodeling expose the promoter?
Because when chromatin decondenses, a region of DNA is exposed, which includes the promoter.
What are the elements genes are composed of?
Coding regions (exons)
Non-coding regions (introns)
Untranscribed regulatory regions (enhancers, promoter, TATA box)
What are regulatory regions?
Sequences of DNA that are recognized by special proteins called transcription factors, which are necessary for initiating transcription by RNA polymerase.
Which element contains sites that can bind to a specific region of the DNA?
Transcriptional factor
Transcriptional factors cannot initiate transcription alone. What does they do instead?
Form a pre-initiation complex with RNA polymerase
What do each of these RNA polymerases produce? RNA pol. 1, RNA pol. 2, RNA pol. 3
1: rRNA
2: mRNA
3: tRNA
What are the three steps to transcription initiation?
- Regulatory transcription factors bind with a DNA sequence called an enhancer.
- Binding of regulatory transcription factors recruits the general transcription factors to the promoter of the gene
- The general transcription factors recruits the components of the RNA polymerase complex, and transcription takes place
(T/F) Each transcription factorsregulates the transcription of a single gene.
False, each transcription actor may regulate the transcription of several genes.
Explain the following statement: Every transcription factor has a DNA-binding domain.
a part of the protein that physically binds to the dsDNA helix.
2T1L:
A:Transcriptional factors often recognize parts of the promoter sequence at the start of a gene and bind to them.
B:They can only block the functioning of RNA polymerase
C:The action of a transcriptional factor can be switched off by an inhibitor molecule.
B: They can either promote or block the functioning of RNA polymerase.
What is an inhibitor molecule?
Can switch off the action of a transcriptional factor. Can bind to the transcriptional factor, preventing it from attaching to DNA, thus stopping the gene from being transcribed.
Certain hormones affect specific cells due to their ability to influence transcriptional factors, and therefore gene expression in the cell. Explain how oestrogen is an example of this.
Oestrogen diffuses across the cell membrane. Once inside the cytoplasm it combines with a site on a transcriptional factor. The hormone changes the shape of the transcriptional factor causing the inhibitor molecule to be released.
Explain alternative splicing.
Which part of the DNA is exposed when chromatin remodeling occurs and why?
The promoter because when chromatin decondenses, a region of DNA is exposed, which includes the promoter
What are the three elements genes are composed of?
- Coding regions (exons)
- Non-coding regions (introns)
- Untranscribed regulatory regions (enhancers, promoter, TATA box)
