Module 35 Flashcards
Regulation of Gene Expressions
What happens when a gene is expressed
The doing of the Central Dogma
A functional product is produced, such as a protein
What is gene regulation
Gene expression does not happen at all times under all conditions
It is the when, where, and how much of gene expression
What allows for cell specialization and for multicellular organisms to develop
Gene regulation
Where
In which cells
When
Under what conditions, environmental conditions, or period of life (development)
Specialization
Different types of cells express different genes
Most cells share the same sets of genes, but different sets of them are expressed
Do skin cells have the genes that encode for isulin
YES, but they are not expressed in these cells
When is insulin expressed in the pancreas
When it receives a signals that the body’s blood sugar levels are high
How does gene regulation help save energy and resources
By not activating all genes at all time
When does gene regulation occur
Anytime during DNA replication
Level of chromosome to even after the protein is made
What are some additional levels of gene regulation that are not possible in eukaryotes
How DNA is packaged into chromosomes, RNA processing, and the separation between transcription and translation,
At what level is gene regulation done in prokaryotes
In the level of transcription
What does gene expression involve in prokaryotes
Transcription of the gene into mRNA and translation of the mRNA into protein
POSITIVE REGULATORY MOLECULE
Binds to DNA at a site near the gene in order for transcription to take place
-usually a protein
-ACTIVATOR
NEGATIVE REGULATORY MOLECULE
binds to the DNA at a site near the gene and prevents transcription
-usually a protein
-REPRESSOR
Activators
Required for RNA polymerase to bind to the DNA strand and turn on the transcription
A Positive regulatory proteins
What two binding sites can DNA have
(both eukaryotes and prokaryotes)
One for the activator and one for the polymerase
What is RNA polymerase called when it attaches to the binding site after the activator
It is the PROMOTER
An Allosteric Effect
When a molecule binds to a protein, changing its shape alters its activity.
What can the allosteric effect cause when an activator is effected
It can result in more transcription of the gene.
Small molecules bind to and change the activity of the activator
How does RNA polymerase bind during negative regulation
RNA polymerase binds on its own to the DNA molecule, allowing transcription to occur.
The negative regulatory protein can bind and turn off transcription
Activator
Required to turn on transcription
A positive regulatory molecule
Promoter
RNA polymerase
Activates the RNA transcription
Repressor
Part of the negative regulatory process
Turns off DNA transcription
Inducer
The small molecule that interacts with the repressor, preventing it from binding to DNA, keeping gene expression turned on
Works through the allosteric effect
What does Beta Galactosidase do
Cleaves lactose into glucose and galactose to become a source of energy and carbon
What is the gene for Beta Galactosidase
lacZ
LacY
Gene for permease
Permease
transports lactose from the external medium into the cell
Allows lactose to be transported into the cell
RNA polymerase promoter in the lactose operon
LacP
Gene organizations where genes are transcribed and expressed together at the same time
An Operon
Gene that encodes for the repressor of the lactose operon
lacI
Where does the repressor protein bind to in the lactose operon
A regulatory DNA sequence called lacO
Operator
A regulator DNA sequence where the repressor protein binds
Why aren’t the genes that encode for proteins that break down lactose transcribed in the absence of lactose
The repressor protein stays attached to the operator in the absence of lactose, so the genes are not expressed
Where do repressor proteins bind at
the operator
where does the RNA polymerase bind at
the promoter
How does lactose act as an inducer in the lactose operon
The isomer that always accompanies lactose prevents the binding of the repressor LacI
The isomer that prevents the binding of the repressor in the lactose operon
Allolactose
What is glucose and galactosidase subunits used for
Energy and carbon sources
Transcription factors
The initial group of proteins that bind to the promoter, then the RNA polymerase, allowing transcription to proceed
Do transcription factors act as positive or negative regulatory molecules?
positive
Enhancer
The regulatory DNA sequence in or near a gene
Regulatory transcription factors
Controls the binding of general transcription factors to the proteins
BINDS TO THE PROMOTER SEQUENCE AND HELPS RECRUIT RNA POLYMERASE
- they are proteins
What two binding sites can regulatory transcription factors have
one that binds to the enhancers (DNA sequence in or near a gene) and one that binds to the general transcription factor(s)
What happens is regulatory transcription factors fail to bring the general transcription factors to a gene
Transcription does not occur
Silencers
A DNA sequence that represses transcription
A gene can be regulated by how many enhancers and silencers
They are typically close to the gene
- multiple enhancers and silencers regulate the gene’
- each enhancer and silencer has one or more regulatory transcription factors that bind with it
How do enhancers and silencers impact transcription of eukaryotic genes
Transcription can only take place when the PROPER COMBINATIOn of regulatory transcription factors are present in the same cell
Transcription depends on the presence of a PARTICULAR COMBINATION of regulatory transcription factors
Combinatorial control
A type of gene regulation within eukaryotes, dependent on the combination and presence of particular enhancers and silencers.
RNA splicing
Exons are joined and introns are removed
Exons
Regions that are retained and expressed in mRNA from the long primary transcript
Introns
Regions of the primary transcript that are removed during RNA splicing
Alternative splicing
The same primary transcript can be spliced in different ways (exon combos) to yield different proteins
What percent of human genes undergo alternative splicing
Over 90%
What does a high affinity for insulin in muscles do and come from
From the excluded 11 exon
Allows the muscle cells to absorb enough glucose to fulfill their energy needs
RNA Editing
When the mRNA acts as a substrate for enzymes
The enzyme will modify certain bases, changing their sequences and what proteins they code for
Many go after amino groups
Amino Groups
-NH2
mall regulatory RNA molecules
Type of noncoding RNA molecules
helps maintain the stability of mRNA
siRNA and miRNA
Small regulatory RNA
Small interfering RNA and microRNA
They can be incorporated into large protein complexes in order to target specific mRNA molecules, DEGRADING RNA TRANSCRIPTS (INHIBITING translation
What does it mean to degrade an RNA transcript
to prevent or inhibit its translation
What are the 5’ UTR and 3’ UTR
untranslated regions that bind with regulatory proteins (and sometimes has binding site for small regulatory proteins)
- helps control the mRNA translation and degradation
How do RNA-binding proteins control where mRNA is translated at
RNA-binding proteins (by transport or repression) cause the mRNA to be translated or degraded only in certain places (the places in which the proteins are present)
What can a resulting protein affect in its cell or organism
It can affect metabolism, signaling, gene expression, and cell structure.
Post-translational modification
After translation, some proteins are modified in multiple ways ( in collective processes) that regulate their structure and function
Why is post-translational modification important to the cell
Some proteins are dangerous and can kill the cell
ex. protease and trypsin can kill the cell, so they must be KEPT INACTIVE (translated in inactive forms) until they are secreted from the cell where they are then made active by modification
aperones
Proteins that help proteins fold
What can happen if a protein doesn’t fold right
It can form an aggregate
What are aggregates
They are destructive to the cell and are associated with many disease
(Alzheimers, Huntingtons disease, and others)
What other post-translational modifications can occur
addition of one or more sugar molecules or of functional groups
Where and why are sugar molecules added in post-translational modification
They are added to the side chains of some amino acids, altering the folding and stability
Where and why are functional groups added in post-translational modification
Change the shape and function of the protein
groups include phosphate, acetyl, methyl
What can the addition of a phosphate group to the side chains of an amino acid do
Key regulator of protein activity
The negative charge alters conformation switching it from inactive to active or the other way around
Chromatin
A complex of DNA, RNA, and proteins
what DNA is packaged in within eukaryotes
Gives chromosomes their structure.
Chromatime Remodeling
Loosens the chromatin to allow space for transcriptional proteins and enzymes to work
- Nucleosomes are repositioned to expose different stretches of DNA to the environment of the nucleus
When chromatin is in its coiled state the DNA is not accessible to proteins that carry out transcription
Nucleosome
The basic repeating subunit of chromatin packaged inside the cell’s nucleus
DNA wound around 8 histones
Histones
What DNA winds up around
Where does modification usually happen (when at the chromatin)
At the histone tails
Histone tail
Strings of amino acids that protrude from the histone proteins in the nucleosome
What happens when a methyl group is added to the Cytosine base
It changes the structure of chromatin, modifies the histone, and the position of the nucleosome (restricting the access of transcription factors to promotors)
Epigenetics
Changes to the manner in which DNA is PACKAGED, not the DNA itself
-can be inherited, reversible, responsive to environmental changes
Imprinting
Sex-specific silencing of gene expression
Imprinted genes (from one parent) are silenced, so only the genes inherited from the other parent are expressed.
