3.1.2 + 3.2.1
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When cAMP is present... (4)
-cAMP binds to CAP
-cAMP/CAP complex bind to the CAP site in DNA
-RNA polymerase binds the promoter efficiently
-transcription occurs frequently
When cAMP is absent (3)
-CAP does not bind to DNA
-RNA polymerase binds the promoter inefficiently
-transcription occurs rarely
(glucose influences formation of CAP/cAMP complex) When extracellular glucose concentrations are high...(4)
-enzyme is inactive
-intracellular cAMP are low
-no CAP binding
-transcription is decreased
-cell continues to use glucose as energy source
(glucose influences formation of CAP/cAMP complex) When extracellular concentrations of glucose are low..(4)
-enzyme is active
-intracellular cAMP concentrations are high
-cell uses lactose, if it is present
What does the enzyme adenyly cyclase produce?
cAMP from ATP
How is adenylyl cyclase inhibited?
by extracellular glucose
What is the outcome of glucose high and lactose low? (4)
-no CAP site
-promoter is bounded loosely
-repressor protein on DNA, blocking transcription
-very infrequent transcription
What is the outcome of Glucose high, LActose High? (4)
-no CAP in the CAP site
-promoter bound loosely
-repressor protein falls off DNA, because lactose is binded
-infrequent trasncription occurs
What is the outcome is glucose is low and lactose is high? (4)
-CAP binds to CAP site
-promoter is binded tightly to RNA polymerase
- -repressor protein falls off DNA
- *lactose binds to it
-frequent transcription occurs
What does regulation of gene expression do? (2)
-allows eukaryotic cells to respond to changes in the environment and;
-causes distinct cell types to develop developmentally
In Eukaryotes, what needs to happen to DNA before trasncription can occur?
DNA must be opened
What does alternative splicing allow a gene to do?
allows a single gene to code for several different products
Once mRNA is in cytoplasm, gene expression is controlled by molecules that regulate the following 3 things
-life span of mRNAs
-the efficiency of translation
-the activation or inactivation of protein products
6 steps of eukaryotic gene expression) 1st step (2)
- open DNA to allow enzymes to access the DNA strand
6 steps of eukaryotic gene expression) 2nd step (2)
- -primary transcript is made
- *pre mRNA
- *still includes introns
6 steps of eukaryotic gene expression) 3rd step (2)
- -make a mature mRNA
- *add the CAP and tail
- *remove the introns
6 steps of eukaryotic gene expression) 4th step (2)
-comes out of nucleus heads to ribosome
6 steps of eukaryotic gene expression) 5th step
-creating a polypeptide
6 steps of eukaryotic gene expression) 6th step (2)
-post translational modification
-modifying the protein
What does a nucleosome structure contain?
WHat charge do histones carry?
a positive charge
WHat do histones contain?
lots of lysines and/or arginines
What charge does DNA have?
What gives DNA its charge?
- phosphate groups
- *they make DNA negative charge
Histones AND DNA
They enjoy interacting with each other because of the opposite charge
What resulted in formation of fibers?
interactions between histone proteins and DNA
What does the histone acetyl transferase (HAT) do? (2)
-opens chromosome for transcription
- attaches an acetyl group to chromosome
Why does HAT attach an acetyl group to chromosome? (2)
- when it attaches an acetyl group, it reduces the number of positive charges on histone
- *makes it uncoil because the electronegativity decreases between DNA and Histone
What is histone deacetyl transferase (HDAC) ? (2)
-packs chromosome closed
- -takes teh acetyl group off the chromosome
- *it makes DNA condense
what do methyl transferases do?
turn on or off a gene
What is epigenetic modulation? (2)
- -turning on or off genes by methylating and acetylating them
- *this can go across generations without changing DNA
What is the TATA binding site in basal promoter region?
it is where TATA binding protein binds that is essential for transcription
What does the promoter proximal element do? (2)
- -has a site that binds specific regulatory proteins that promote specific gene trasncription
- **right next to promoter region
- no regulatory protein no gene expression
What are enhancer sites?
if a regulatory protein binds here (regulatory site) it greatly enhances transcription
Can enhancers be located in an intron?
What are silencer sites?
binding of different proteins to the regulatory sites like silencer sites, significantly reduce transcription
4 steps that extracellular signals trigger cell-specific expression
1. signal arrives at cell with message "become a muscle cell"
2. signal transduction results in production of intracellular signal
3. Regulatory proteins are produced or activated in response to intracellular signal
4. regulatory proteins bind to regulatory sites in DNA, triggering expression of muscle-cell specific genes
Alternate splicing in eukaryotic cells allow it to..
have one gene that encodes for a number of different but related proteins
*ex) codes for smooth muscle and skeletal muscle in same gene but only splices the smooth muscle
What is more important, number of genes or the variiety of the genes?
- the variety of genes.
- *it is more important how many proteins in different variance we can produce
smal specific pieces of RNA can ultimately lead to the destruction of other mRNA that is out in a cell
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