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Prokaryotic Gene Regulation Part 1
Terms in this set (21)
Why regulate genes?
1. control the order and disorder in the cell
2. respond to external and internal stimuli
1. order vs disorder
a. Example: gene produces enzymes and since conflicting biochemical occur in the cell, a problem occurs, so why regulate gene in the cell?
2. Respond to external and internal stimuli
1. cells are order systems and if the cell is disorder then it will no longer be a cell thus die.
a. gene regulation prevents complex chemistry inside the cell from going arise.
2. turning a gene on, only when it detects something outside or inside a cell (event, chemical species, light, and etc.), the cell use gene activation to respond to stimuli.
Gene Regulation - How?:
What are the 4 Types of Gene Regulation and their function?
1. Transcriptional: regulates transcription to be induced or prevent mRNA synthesis.
- prevent protein from being made since there is no mRNA to be translated
2. Post-transcriptional: regulate the destruction of mRNA by a cell in a species.
- happens after transcription completes.
3. Translational: regulate prevention of translation (control protein synthesis).
- prevent initiation or halt elongation of translation thus preventing the protein from being made. mRNA will still be present.
4. Post-translational: regulate the destruction or modification of protein
Why is transcriptional the most common?
the other three regulations will be less energy proficient if the cell system regulates the genes at those levels.
- in transcription regulation, preventing the formation of mRNA save energy from polymerization from mRNA and protein synthesis.
Explain how post-translation modification can use up energy and how it related to transcriptional to occur mostly?
In post-translational modification occur the cell makes mRNA -> mRNA translated into protein -> protein destroyed
- the gene is being silenced and cost the cell a lot of energy to get nothing
Transcriptional gene regulation
- where does it occur?
regulation of a gene at the level of whether that gene is transcribed or not
- occur at the promoter level (-10 and -35 region)
region of a DNA in an operon at the promoter to which the repressor binds when the operon is "turned off"
activator binding site
site on DNA where activator binds and controls transcription "turns on"
A protein that suppresses the transcription of a gene.
a protein that binds to DNA and stimulates transcription of a gene
Transcriptional Gene Regulation:
a. What happens when there is no activator and repressor present?
(talking about binding and what it allows)
b. repressor present
(where does it bind to, what does it prevent, and what happen to the enzyme)
c. activator present
where does it bind to, what does it do, and what happen to the enzyme
a. the activator cannot bind to the activator binding site and the repressor can't bind to the operator. This allows the RNAP to bind the -10 and -35 region (promoter). Basal level transcription
b. repressor bind to the operator and it positions the operator differently so that it prevents initiation of transcription, ao RNAP holoenzyme can't assemble in the promoter. "turn off"
c. activator bind to the activator binding site and stabilize the recruit, of RNAP holoenzyme to promoter because it has a stable configuration and bound to DNA: increased activated level. "turn on"
How does the activator work:
a. what does the activator binding site have (what does it generate)?
- because of this.....enhance what ability?
a. activator binding site generates isomerization to change the shape of the polymerase.
- enhance the ability of the polymerase to melt to a promoter at -10 and enhance the ability to do transcription
1. In eukaryotes, what else the activator can do?
- where is the activator and what can it do? (how does the shape affect transcription).
- how does it changes DNA shape?
1. they can change the shape of DNA
- far away from the promoter and and changing the shape can stabilize the process of transcription or inhibit.
- DNA binding protein recruited to change shape
what does the promoter act like in gene regulation?
act like a integration device so it act as an biochemical device that take 2 information from different input and combine them to make an output. This is called logic gates
1. what does the cell use logic gates for?
- what does it turn the input or environment?
1. use logic gates to compute from their environment (or inputs) in the form of binding events of other proteins.
- turns into output in a form of transcription the translational
To sum up how do regulation work in gene?
compute the best response to the environment expressing gene and have protein turn "off" and "on" genes.
- what does it consist of?
the operon that controls the metabolism of lactose
- cap site, operator, promoter between cap site and operator, three structural genes: lac Z, lac Y, and lac A
CAP site (in lac operon)
a. when is it CAP protein present
b. what is it function?
c. why is the CAP site exist (basically what happens if glucose is present and what does this site do when glucose is gone?)
catabolite activator protein
a. produced when glucose level drops
b. "on" switch that induced expression of non-glucose using operon when glucose is gone
c. cell wants glucose so if it is present, the cell will consume sugar, and the cell attempts to turn off the expression of all their carbon source.
if glucose is gone, cell turn on all of the non-glucose gene and control mechanism to decide which one to use.
Operator (lac operon)
lacI repressor site so lacI repressor protein binds to the operator
3 structural genes of lac operon:
1a. function (hint: beta-galactosidase)
1b. what is lactose made of and what the enzyme do?
1c. isomerization: function and what role it plays
2a. function (hint: permease)
2b. why does this gene need permease?
- what must the cell do before using permease
3a. function (beta galactoside transacetylase)
3b. what sugar does it work on?
1a) beta-galactosidase break down lactose into glucose and galactose
1b) lactose disaccharides consist of glucose and galactose and beta-galactosidase break the bonds between two sugar and the sugars proceed to glycolysis or other pathways
1c) isomerizes lactose to allolactose which plays a role in activating lacI repressor
2a) encodes lactose permease - transport lactose
2b) permease exists internally so to use sugar, a cell must bring it to itself then digest ur where the cell gets the enzyme.
- enter in lactose before it can be acted upon.
3a. beta galactoside transacetylase acetylates disaccharides for reason unknown
3b. acetylated a disaccharide that contain galactose
- why lacI need a permease?
tunnel for a specific molecule to be transported from the cell to the membrane
- lactose is a disaccharide with 12 C and a lot of hydrogens and oxygen atoms and the hydrogen into OH group so lactose is large and polar. Large and polar won't pass through the membrane sp it needs a permease
Recommended textbook explanations
Lehninger Principles of Biochemistry
David L Nelson, Michael M. Cox
Fundamentals of Biochemistry
Charlotte W. Pratt, Donald Voet, Judith G. Voet
Campbell Biology (AP Edition)
Cain, Jackson, Minorsky, Reece, Urry, Wasserman
Biocalculus: Calculus for the Life Sciences
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