Regulation of Gene Expression Flashcards
Group of structural and regulating genes that function as a single unit
Operon
Gene that codes for the amino acid sequence of a peptide or protein
Structural Gene
4 parts of the operon
Regulator Genes
Promoer
Operator
Structural Genes
Normally located outside the operon, this codes for a DNA-BINDING protein that acts as a repressor
Regulator gene
Signals the start of the operon and location where transcription begins
Promoter
In an operon, Protein molecule that binds to an operator, preventing transcription of structural genes.
Repressor
Short portion of DNA located before the structural genes
Operator
These genes code for the Enzymes and Proteins involved in the metabolic pathway of the operon
Structural Genes
How are trp operons regulated
When tryptophan is present in the system it binds to a repressor allowing it to attach to the operon
Stopping the production of more tryptophan
Are operons in Pro or Eukaryotes
Prokaryotes
Are operons in Pro or Eukaryotes
Prokaryotes
If lactose is present how does this affect the lac operon function?
Lactose binds to the repressor stopping it from binding with the operator
Molecule that brings about activity of an operon by joining with a repressor and preventing it from binding to the operator
Inducer
Lactose is what to the lac operon?
What does it do?
Inducer
Lactose prevents the repressor from binding to the operator allowing for RNA polymerase to bind to the operator allowing for transcription to occur
Which type of pathways are Inducible operons found in?
Catabolic Pathways
What is a catabolic pathway?
One that breaks down a substance
What is the difference between the role of the promoter and the operator in an operon?
Promoter is the location of transcription initiation
The operator is a segment of DNA that regulates whether the structural genes will be transcribed
How does Gene expression differ in an inducible operon vs a repressive operon?
Repressive openron is normally on and turned off by the action of a repressor
Inducible operon us normally off and is turned on by an environmental condition
Describe the difference between positive control and negative control of gene expression
Positive control is transcribed when it is regulated by a protein that is an activator Not a repressor
Negative control is not transcribed when it is regulated by a protein that is a repressor
Which operon of trp/ lac is catabolic / anabolic
trp operon is anabolic ( it builds tryptophan)
lac operon is catabolic (metabolizes lactose)
5 primary levels of control for gene expression of eukaryotes
Chromatin structure
Transcriptional control
Posttranscriptional control
Translational control
Posttranslational control
Chromatin packing is used as a way to keep genes….
Turned off
Why does chromatid packing affect gene expression
RNA polymerase cannot access the genes
Chromatin structure is one example of epigenetic inheritance, what is epigenetic inheritance?
Inheritance doesn’t only come from DNA
But also from parents experiences
Parental experiences can be passed to offspring in the form of epigenetic tags
The degree to which a gene is transcribed into mRNA determins the amount of gene product
In the nucleus, transcription factors may _____ or _____ transcription, the first step in gene expression.
Transcriptional control
Promote / Supress
Involves mRNA processing and how fast mRNA leaves the nucleus
Posttranscriptional control
Occurs in the cytoplasm and affects when translation begins and how long it continues
Translational Control
Takes place in the cytoplasm, Occurs after protein synthesis. Only a functional protein is an active gene product
Posttranslational Control
Network of DNA strands and associated proteins observed with a nucleus of a cell
Chromatin
Tightly packed chromatin is called?
Loosely packed?
Which is more associated with active genes?
Heterochromatin = tightly packed
Euchromatin = loosely packed
Euchromatin is more associated with active genes
What works on Euchromatin to make the DNA more available, and the promoter accessible for transcription?
Chromatin Remodeling Complex
What is a DNA-Histone complex called?
Nucleosome
Which type of histone tail contains
Methyl Group (-CH³)
Acetylated (-COCH³)
Methyl Group Hetrochromatin
Acetylated Euchromatin
2 ways on which the chromatin remodeling complex affects gene expression
- Physically moving nucleosomes to expose promoters
2. Adding acetyl or methyl groups to histone tails
Barr body is which type of chromatin?
What is a barr body
Hetrochromatin
An inactive X chromosome
Protein that participates in the initiation of transcription by binding to the enhancer regulatory regions
Transcription activator
DNA sequence that acts as a regulatory element to increase the level of transcription when regulatory proteins, such as transcription activators, bind to it
Enhancer
What act as a bridge between transcription factors and transcription activators at the promoter
Mediator protein
What does Posttranscriptional control do?
Gene expression following transcription that regulates the way mRNA transcripts are processed
Protease do?
Where are they found?
Break down proteins
Regulate how long protein is active in cell
Proteasomes and lysosomes
Posttranslational control affects
Activity of a protein product
Post script for where an enzyme is stored
Somes
Ie. Lysosome
A permanent change in the base sequence
Gene mutation
Spontaneous mutations aka
Replication errors
Induced mutations caused by
Mutagens
Point mutations is…
Changing 1 single DNA base
Frameshift mutation
1 or 2 nucleotides are inserted or deleted from DNA
CATASTROPHIC
Lac operator is an example of which kind of control?
What happens when lactose is present?
When the repressor is removed what happens?
What does this enzyme do?
Positive control
DNA Polymerase makes a code for Lactase.
Breaks down lactase
The trp operon is what kind of control?
What happens to the repressor when tryptophan is not present?
When tryptophan is present what happens with the repressor?
Negative control
The repressor is not attached to the operator allowing for DNA polymerase to make Tryptophan
The reporesor is on the “on” posistion
Where does the Repressor attach?
Operator
How do prokaryotes stop making tryptophan?
What process happens?
The they have tryptophan it binds to the repressor protein which stops DNA polymerase from coding for more.
Carcinogenisis begins with the loss of this type of gene activity and the gain of this type of gene activity
Tumor Suppressor
Oncogene
When tumor Suppressor genes are inactive and oncogenes are active what occurs?
Uncontrollable Cell Division
Tumor Suppressor and proto-oncogenes code for _____ _____
Transcription Factors
The operon model states that regulator genes code for ________
Repressors
When a repressor binds to the ______, RNA polymerase is is unable to bind to the ______
Operator / Promotor
When RNA polymerase is unable to bind to the promoter, transcription of the ______ _______ of the operon cannot take place
Structural Genes
trp operon is an example of a _________ operon because when tryptophan is present it binds to the repressor causing it to bind to the operator stopping transcription
Repressible
The lac operon is an example of an _______ operon when lactose (the inducer) is present it binds to the repressor cause it Not to bind with the operator allowing for transcription
Inducible
Both lac and trp operon exhibit ______ control
Why?
Negative
The repressor is involved
What type of chromatin are exemplified by lampbrush chromesomes in vertebrates?
Euchromatin
DNA sequences called ______, play a role in transcriptional control in eukaryotes
Enhancers
Regulatory proteins called ______ ______, play a role in transcriptional control in eukaryotes
Transcription Factors
Transcription factors bind to ________
Transcription Activators bind to _______
Promoter
Enhancer
What is involved in RNA interference?
microRNAs, Small Interfering RNAs
Type of control that affects whether or not an enzyme is active and how long it is active
Post translational control
