13: Regulation of Gene Expression Flashcards
Module 3, Lesson 2
The process of converting genetic information into a genetic product (usually a protein) is…
Gene expression
Prokaryotes regulate their gene expression to…
Respond to environmental changes
Eukaryotes regulate their gene expression to…
Progress through developmental stages and maintain homeostasis
List the three means by which organisms can regulate gene expression.
- Transcriptional regulation
- Post-transcriptional regulation
- Post-translational regulation
Which method(s) of regulation can only occur in eukaryotes?
Post-transcriptional
because this occurs as mRNA is moved out of the nucleus, which prokaryotes do not have
The first opportunity for cells to control gene expression is…
Transcriptional regulation
The most common form of regulation in cells is…
Transcriptional
Transcriptional regulation depends on…
RNA polymerase interacting with DNA
Transcriptional regulation is controlled by…
Binding proteins
(“transcription factors”)
The ____ contains the binding site for regulatory proteins that affect the cell’s ability to perform transcription.
Promoter
The region of the promoter where RNA polymerase binds to the DNA is the…
Core promoter
Proteins that affect the ablity of RNA polymerase to bind to the promoter or start transcription are…
Regulatory proteins
True or false:
In eukaryotic cells, each gene has its own promoter sequence.
True
True or false:
In prokaryotes, a single promoter can control multiple genes.
True
Regulatory proteins that help recruit RNA polymerase to start transcription are called…
Transcriptional activator proteins
(or simply “activator proteins”)
The process by which a regulatory protein promotes transcription is…
Positive control
A protein that binds to a gene in such a way as to prevent RNA polymerase from binding is called a…
Transcriptional repressor protein
(or simply “repressor protein”)
The process by which a regulatory protein inhibits transcription is…
Negative control
True or false:
Genes can have positive or negative control, but not both.
False
A gene or operon can have positive control, negative control, or both.
A cluster of genes with related functions that are controlled by a single promoter is called a(n)…
Operon
Prokaryotes are able to respond quickly to environmental changes because…
Their genes are organized into operons
List the three regions that an operon may have.
- Core promoter
- Activator binding site
- Operator
The ____ region of an operon is bound by the sigma factor of RNA polymerase.
Core promoter
True or false:
All operons have a core promoter region.
True
The DNA binding site for an activator protein is called the…
Activator binding site
True or false:
All operons have an activator binding site.
False
Only operons that exhibit positive control can have activator binding site(s).
The DNA binding site for a repressor protein is called a(n)…
Operator
True or false:
All operons have an operator.
False
Only operons that exhibit negative control can have operator(s).
In prokaryotes, the proteins needed for lactose metabolism are encoded in the…
lac operon
What type(s) of control does the lac operon exhibit?
Positive and negative
In the lac operon, the CAP activator promotes transcription when…
Lactose is present
In the lac operon, the lac repressor protein inhibits transcription when…
No lactose is present
The lac operon can only perform transcription when…
Lactose is present AND glucose is absent
What happens in a lac operon when both lactose and glucose are present?
The lac repressor is released, but the CAP activator does not bind to the DNA.
because glucose is the cell’s preferred food source
The trp operon contains all the genes needed to produce…
Tryptophan
(an amino acid)
What type(s) of control does the trp operon exhibit?
Negative
The trp operon does not perform transcription when…
Tryptophan is present in the environment
The trp operon performs transcription when…
No tryptophan can be acquired from the environment
How does the trp operon exhibit negative control?
When tryptophan is present, it binds the the trp repressor protein, enabling it to bind to the operator sequence.
____ occurs when transcription is stimulated by molecules in the environment.
Induction
____ occurs when transcription is inhibited by molecules in the environment.
Repression
In addition to positive and negative control, the lac operon exhibits…
Induction
(the presence of lactose causes the lac repressor protein to be released from the DNA)
In addition to negative control, the trp operon exhibits…
Repression
(the presence of tryptophan causes the trp repressor protein to bind to the DNA)
Induction and repression occur when…
An external molecule causes or stops transcription by interacting with a regulatory protein
Positive and negative control refers to…
The type of protein that regulates transcription
List the two types of transcription factors.
- General
- Specific
True or false:
General transcription factors are only found in eukaryotes.
True
Eukaryotes require general transcription factors in order for…
The minimum (basal) amount of transcription to occur
List three ways eukaryotes can use general transcription factors to regulate transcription.
- Changing the availability of the transcription factors
- Altering the TFs’ ability to bind to DNA
- Altering the TFs’ ability to interact with RNA polymerase
____ are needed to increase transcription past the basal level.
Specific transcription factors
True or false:
Specific transcription factors are found in both prokaryotes and eukaryotes.
True
True or false:
A specific transcription factor will always bind at or near the core promoter.
False
Eukaryotes in particular may utilize other binding sites.
Some specific transcription factors bind to DNA regulatory regions called…
DNA enhancer elements
Why do specific transcription factors not always bind to the core promoter in eukaryotes?
Their genomes are much bigger.
In eukaryotes, DNA and histone proteins are packaged into bead-like structures called…
Nucleosomes
Nucleosomes are then assembled into…
A chromatin structure
Why do eukaryotes package their DNA?
So that all the DNA is able to fit into the nucleus.
When DNA becomes wound around histone proteins, it becomes ____ for transcription machinery to access it.
Harder
____ can be modified to change how tightly DNA is wound around them.
Histone proteins
____ is a process that loosens DNA by adding an acetyl group.
Acetylation
The structure of nucleosomes can be altered by…
ATP-dependent enzymes
List three ways in which ATP-dependent enzymes can change nucleosomes.
- Sliding
- Moving up/down DNA
- Remodeling
Remodeling involves altering…
How DNA interacts with histone proteins
____ regulation occurs while the cell is preparing mRNA for translation.
Post-transcriptional regulation
Which type of gene regulation only occurs in eukaryotes?
Post-transcriptional
List four methods of post-transcriptional gene regulation.
- mRNA alternative splicing
- Inhibition of transport from nucleus
- Inhibition of translation
- mRNA regulation by small RNAs
Alternative splicing is the process of…
Causing one mRNA to code for different proteins
Some mRNA sequences can be spliced in multiple ways, enabling them to…
Code for more than one protein
Alternative splicing has been observed in the…
Thyroid and hypothalamus
It is believed that only around ____% of the mRNA produced is exported and translated.
5%
List two ways that the cell can limit the amount of mRNA that is translated after it has left the nucleus.
- Limiting the availability of proteins needed for translation
- Producing proteins that prevent specific mRNA from being translated
List the two classes of small RNAs that can interfere with mRNA translation.
- Micro RNAs (miRNAs)
- Small-interfering RNAs (siRNAs)
Micro RNAs are formed when a single-stranded RNA folds to make a small segment of…
Double-stranded RNA
Micro RNA strands are…
Self-complementary
Micro RNAs are usually encoded in the…
Genome
Small-interfering RNAs are made from long segments of double-stranded RNA that are…
Cut into small segments
List two ways in which siRNAs can be formed.
- Produced by the cell through pairing of 2 mRNAs
- Introduced from the environment
Small RNAs interact with proteins to form a complex called…
RISC
After binding to the complementary region on a target mRNA, the proteins in RISC…
Block translation or degrade the mRNA
____ is a research method that introduces specific segments of double-stranded RNA to selectively control gene expression.
RNA interference
(RNAi)
RNAi allows researches to analyze the effects of ____ on an organism.
Gene loss
Post-translational gene regulation involves…
(two items)
- Modification of proteins
- Degradation of proteins
Post-translational regulation occurs…
After mRNA has been made into proteins
List three methods of modifying proteins.
- Adding/removing a phosphate group
- Adding carbohydrates
- Adding lipid groups
The addition or removal of a phosphate group is especially important for…
Enzymes
The addition or removal of a phosphate group is called…
Phosphorylation or dephosphorylation
The addition of carbohydrates is especially important for…
Cell identity proteins
The addition of a carbohydrate is called…
Glycosylation
The addition of lipid groups is especially important for…
Anchor proteins in the cell membrane
Cells can systematically target and degrade proteins by…
Adding ubiquitin
After a protein has been ubiquinated…
It is broken down into polypeptide fragments by the proteasome
True or false:
The ubiquitin is also degraded by the proteasome.
False
It is cleaved from the protein and released to be used again
Because of regulation, gene expression is…
Very tightly controlled
Transcriptional regulation controls…
Which genes are transcribed
Transcriptional regulation is performed by…
Transcription factors and the accessibility of DNA
Post-transcriptional regulation controls…
Which genes are translated
Post-transcriptional regulation is performed by…
mRNA processing and translation inhibition
Post-translational regulation controls…
The activity of translated proteins
