Unit 2: Gene Regulation Flashcards
gene regulation
- various ways in which cells control gene expression
what are the characteristics of gene expression (3)
- where (in which cells) are genes turned on
- when (during development or in response to changes in the environment) are they turned on
- how much gene product is made
positive regulation
- process where a regulatory molecule (usually a protein) must bind to the DNA at a site near the gene in order for transcription to take place
negative regulation
- process where regulatory molecule (usually a protein) must bind to DNA site near the gene to prevent transcription
What sequence do eukaryote promoters contain and where are they located? (2)
- 5’-TATAAA-3’
- about 25-35 base pairs upstream from the transcription start site
Where are prokaryote promoters located and what are they called? (2)
- about 10 and 35 base pairs upstream of the transcription start site
- -10 and -35 sequence motifs
transcriptional activator
- regulatory protein/compound that increases activity of an enzyme
What are the 2 binding sites that DNA contains?
- an activator protein binding site and the RNA polymerase complex binding site
In positive regulation, what occurs when the activator is successfully recruited to a site near the RNA polymerase promoter?
- RNA polymerase can bind to the promoter
In positive regulation, what occurs when the activator is unsuccessfully recruited to a site near the RNA polymerase promoter?
- RNA polymerase cannot bind and transcription does not occur
Where can the binding site for the activator be in positive regulation?
- upstream of the promoter, downstream of the promoter, or even overlap the promoter
allosteric effect
- change in the activity or affinity of a protein as the result of binding of a molecule to a site other than the active site
Why do activators change shape in different situations? (2)
- small molecules can bind to activators to change their shape so that they can bind to DNA
- small molecules can bind to activators to change their shape so they can no longer bind to DNA
repressor
- a protein that, when bound with a sequence in DNA, can inhibit transcription
In negative regulation, what occurs when there is no repressor bonded to the repressor bonding site?
- this allows RNA polymerase complex to be recruited and transcription takes place
In negative regulation, what occurs when there is a repressor bonded to the repressor bonding site?
- the repressor inhibits the recruitment of RNA polymerase and transcription does not occur
Where can the binding site for a repressor be located relative to a promoter?
- upstream, downstream, or overlapping with the promoter
inducer
- small molecule that elicits gene expression by changing the shape of repressors so they cannot inhibit transcription
what is the relationship between a strong promoter, a weak promoter, and a consensus sequence?
- strong promoters are closer to consensus while weak promoters are further from consensus
What is transcriptional control?
- controlling the amount of transcription via promoter strength and regulatory proteins
What is translational control?
- controlling the amount of translation by altering how fast a mRNA survives in the cell (for example by changing the length of the poly-A tail)
What is post-translational control?
- modifying enzymes directly by changing their shape or blocking active sites
constitutive gene expression
- when genes are expressed all the time (genes that code for RNA polymerases, ribosomes, tRNA, etc)
- this does not mean that there are high levels of expression
Although two different genes are constitutively expressed, how can their level of transcription and translation differ?
- promoter strengths may be different resulting in different amounts expressed
- the RNA made may have different half lives which would results in different amounts of translation
