Gene Expression
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691 Terms
What is gene expression?
Overall process by which the information encoded in a gene is converted into an observable phenotype (most commonly production of a protein).
Why is gene expression regulated?
To adjust to sudden changes 2. To conserve energy 3. To save resources
What does gene expression refer to?
The processes in which the information present in a gene becomes an observable phenotype.
What usually occurs during gene expression?
Production of proteins.
What are the processes involved in the central dogma in molecular biology?
- Transcription 2. Translation 3. Expression of the gene into a phenotype
What happens during transcription?
The gene is transcribed.
What happens during translation?
The transcribed information is translated.
What is the result of gene expression?
The expression results in what is called a phenotype.
Why must cells regulate gene expression?
Cells are not always in a static environment and the environment surrounding the cell constantly changes.
How do cells adapt to changing environmental conditions?
- Activating or “kickstarting” what is already present inside the cell 2. Pulling out the necessary machinery 3. Producing large amounts of needed components in response to what is being sensed
Why must energy usage be calibrated in cells?
Adaptation requires energy expenditure and the cell cannot afford to use energy carelessly.
How is gene expression regulation connected to energy conservation?
The cell must save resources whenever possible.
What must a cell do when placed in an unsuitable condition?
- Determine what machinery is applicable 2. Activate only the machinery needed to survive 3. Resist or withstand the unsuitable condition 4. Still survive and adapt
How does the cell save energy during resource allocation?
The cell saves energy by allocating it only when needed.
What is gene expression the combined process of?
- The transcription of a gene into mRNA 2. The processing of that mRNA 3. Its translation into protein
How is gene expression described?
A multi-combinatorial process.
What are the main processes involved in gene expression?
- Transcription of the gene into mRNA 2. RNA processing 3. Translation into protein
What happens during transcriptional control?
The information encoded in the DNA is copied or transcribed to produce a transcript.
What is produced during transcription?
A primary transcript.
What represents the first transcriptional control?
The production of the primary transcript.
What components are involved in transcriptional control?
- Regulatory proteins 2. Activators 3. Repressors
Why is RNA processing necessary?
Producing a transcript alone is not enough.
Why does the transcript require RNA processing in eukaryotes?
The transcript must safely pass from the nucleus into the cytoplasm.
What is RNA processing control?
The stage where the transcript undergoes processing.
Where does translational control occur?
Outside the nucleus in the cytoplasm.
What happens during translation into protein?
- A ribosome docks onto the transcript 2. The ribosome looks for the corresponding amino acid 3. The amino acid pairs with a codon 4. The pairing leads to the formation of a peptide
What processes have a tandem relationship in gene expression?
- Transcription and translation 2. Transcriptional control and translational control
What is the end pathway of gene expression?
Production of proteins.
At what levels can gene regulation occur?
- Control during processing 2. Control during conveyance or transport 3. Control during translation itself
Why are there multiple levels of gene regulation?
To tightly regulate gene expression.
What does gene expression encompass?
- Processes occurring during the transcription level 2. Processing and pre-processing steps
What is included in post-transcriptional processing?
Processing of transcripts.
Why is post-transcriptional processing especially important in eukaryotes?
Eukaryotic systems include additional processing control mechanisms.
What carries the information coded in the DNA after transcription?
The transcript.
What does the pathway leading to protein formation produce?
A peptide.
What may be included in the pathway leading to protein formation?
An additional layer of translational control.
How is gene expression regulation described in the diagram?
Gene expression is tightly regulated from the onset or start of transcription throughout the translation process.
What are the differences between prokaryotic and eukaryotic gene expression?
- Absence of operons 2. Complexity 3. Different cell types 4. Uncoupled transcription and translation 5. Chromatin structure
Why do differences exist between prokaryotic and eukaryotic gene expression?
Both organisms are structurally different.
How is the bacterial chromosome arranged in prokaryotes?
The bacterial chromosome has no membrane separating it from the rest of the cytosolic components and is structurally exposed within the cytoplasm.
Why do transcription and translation occur simultaneously in prokaryotes?
Because there is no membrane separation.
How does promoter control differ in eukaryotes?
One promoter can control one series of genes.
Why are regulatory proteins in eukaryotes described as being far away from genes?
Because of the structural looping of the eukaryotic chromosome.
How does the complexity of gene regulation differ between bacteria and eukaryotes?
Bacteria have a straightforward system while eukaryotes have a more complex system.
What happens when a promoter is activated in bacteria?
- Transcription 2. Translation of the gene
What components are involved in prokaryotic operon regulation?
- A promoter 2. Regulatory proteins 3. An operon
What can activation of a regulatory or repressor protein lead to in bacteria?
- Turning on the operon 2. Transcription of the operon 3. Turning off the operon
How is gene regulation in bacteria described?
Very straightforward.
What happens to the transcript after transcription in eukaryotes?
The transcript undergoes RNA processing.
Why is polyadenylation important in eukaryotes?
The poly-A tail helps the transcript pass through the nuclear pore more easily.
Where are chromosomes located in prokaryotes and eukaryotes?
- In prokaryotes, the chromosome is scattered throughout the cytoplasm. 2. In eukaryotes, the chromosome is contained inside the nucleus.
What is the effect of the nuclear membrane on eukaryotic gene expression?
There is no simultaneous tandem process of transcription and translation in eukaryotes.
What happens during simultaneous transcription and translation in prokaryotes?
- The ribosome can bind right away 2. The ribosome binding site can immediately bind 3. Translation can immediately begin
What must happen before translation in eukaryotes?
The transcript must first be processed.
What is the role of operons in prokaryotes and eukaryotes?
- Operons are generally applicable to prokaryotes 2. Operons are not present in eukaryotes
What is considered a hallmark of the prokaryotic genome?
The presence of the operon.
How are transcription and translation related in prokaryotes and eukaryotes?
- In prokaryotes, transcription and translation are coupled and simultaneous 2. In eukaryotes, transcription and translation are separated
How does RNA processing help eukaryotic transcripts?
The processing helps the transcripts pass through the nucleus into the cytosol.
Where does protein synthesis occur in eukaryotes?
In the cytosol.
What happens after a eukaryotic transcript crosses the nuclear pore?
The transcript is picked up by the ribosomes for translation machinery.
How does chromatin structure differ between prokaryotes and eukaryotes?
- In prokaryotes, the chromosome is not associated with proteins 2. In eukaryotes, the chromosome is tightly wound around histones
What is formed when eukaryotic chromosomes are tightly wound around histones?
Chromatin organization.
How does chromatin organization affect gene regulation in eukaryotes?
The DNA is not readily available for reading or transcription, creating another layer of complexity in gene regulation.
What controls eukaryotic gene expression?
- Cis-trans acting elements 2. Transcriptional activation/repression 3. Chromatin modifications 4. Gene rearrangement 5. Gene amplification 6. Posttranscriptional modifications 7. RNA stabilization 8. Regulation by noncoding RNA 9. Post translational modifications 10. Protein degradation
What are the major regulatory mechanisms involved in eukaryotic gene expression?
- Cis-trans acting elements 2. Transcriptional activation through repression 3. Modification of the chromatin structure itself 4. Coupling of amplification and rearrangement 5. Post-transcriptional modification 6. Post-translational modification 7. RNA stabilization 8. Protein degradation
What are cis-acting elements?
Elements found within the DNA itself.
What are examples of cis-acting elements?
- Promoters 2. Enhancers 3. Silencers
What is the role of cis-acting elements?
These DNA sequences act as regulatory control regions.
What are trans-acting elements?
Associated proteins at the transcription level.
What are examples of trans-acting elements?
- Transcription factor IIB 2. Activators 3. Repressors 4. Other transcription factors
What do trans-acting regulators do?
- Promote transcription 2. Inhibit transcription
Why is chromatin modification necessary in eukaryotes?
The DNA is not readily available for read-through or transcription.
What is the purpose of chromatin modification?
Modification allows access to DNA from its associated proteins.
What additional regulatory mechanisms are involved in gene regulation?
- Gene rearrangement 2. Gene amplification
What is post-transcriptional modification?
Modifications that occur after transcripts are produced.
What is an example of post-transcriptional modification?
Addition of polyadenylation to transcripts.
Why must transcripts be modified in eukaryotes?
- To pass through the nuclear pore 2. To be picked up by the ribosomal assembly
What is post-translational modification?
Proteins undergo modifications after translation.
What are examples of post-translational modifications?
- Acetylation 2. Glycosylation 3. Methylation
What is the purpose of adding functional groups to proteins?
- Become fully functional 2. Serve its intended purpose
What is RNA stabilization?
The process of stabilizing the mRNA transcripts.
Why is RNA stabilization needed?
There is a need to stabilize the transcripts.
What is the role of protein degradation in gene expression?
Protein degradation can be used as a means to control gene expression.
Why does the cell degrade excess proteins?
Excess proteins that are no longer needed are degraded.
What is the purpose of protein degradation?
To maximize the utility of cellular components and resources.
Why is protein degradation important during changing environmental conditions?
Proteins produced earlier may no longer be needed.
What role does chromatin biology play in gene regulation?
The biology of the chromatin structure itself plays an important role in regulating the expression of genes.
Why does eukaryotic gene expression have a higher degree of complexity?
Eukaryotic gene expression involves different levels of control.
What does gene amplification mean in eukaryotes?
Some genes in the eukaryotic genome may have multiple copies.
What future topics related to gene regulation were mentioned?
- Epigenetic modifications 2. Involvement of class 1 and class 2 transcriptional activators
From what level to what level does regulation occur in eukaryotic gene expression?
From transcriptional regulation up to translational regulation.
What do all gene expression controls still follow?
The central dogma in biology.
Where is genetic information embedded?
Within the DNA.
What does the information in DNA code for?
Genes.
What are the types of genes?
- Structural genes 2. Regulatory genes
Why is transcription necessary?
Since DNA bears the genetic information, the information must be copied or transcribed.
What is transcription?
The copying process of genetic information.
What are the products of transcription?
- Transcript 2. mRNA 3. Messenger RNA
What is the role of messenger RNA?
The messenger RNA is a faithful copy of the code from the DNA.
Why is translation necessary?
For the information to become an observable phenotype.