2 Réplication De L'Expression Génique Flashcards
Qu’est-ce que la différenciation chez l’homme?
La différenciation chez l’homme est irréversible; une fois une cellule spécialisée, elle perd la capacité d’assurer d’autres fonctions.
Que signifie l’équivalence génomique?
Toutes les cellules d’un organisme pluricellulaire possèdent le même génome, mais elles n’expriment pas les mêmes gènes.
Qu’est-ce que l’épissage alternatif?
L’épissage alternatif permet aux cellules d’accumuler des ARN et des protéines spécifiques, chaque type cellulaire exprimant un ensemble de gènes qui lui est propre.
Quel est le rôle du contrôle de l’expression génique?
Il permet à la cellule de modifier l’expression de ses gènes en réponse à un signal externe.
Chez quels organismes a lieu l’expression génique?
L’expression génique n’a lieu que chez les eucaryotes.
Qu’est-ce que la maturation de l’ARN?
La maturation de l’ARN inclut l’épissage alternatif.
Qu’est-ce que la maturation de la protéine?
La maturation de la protéine inclut l’ubiquitination.
Quels sont les 6 étapes de régulation de l’expression génique?
1) Structure de la chromatine; 2) Initiation de la transcription; 3) Maturation de l’ARN; 4) Durée de vie de l’ARNm; 5) Initiation de la traduction; 6) Dégradation de la protéine.
Quels facteurs influencent la structure de la chromatine?
Les modifications épigénétiques comme l’acétylation des histones et la méthylation des îlots CpG.
Quels sont les éléments impliqués dans l’initiation de la transcription?
Les facteurs de transcription généraux et spécifiques.
Comment la durée de vie de l’ARNm est-elle régulée?
Elle est régulée selon les 3’UTR et l’ARN interférence.
Quel est le rôle de l’ARN interférence dans l’initiation de la traduction?
L’ARN interférence (miARN) et les protéines régulatrices influencent l’initiation de la traduction selon les 5’UTR ou 3’UTR.
Comment se fait la dégradation de la protéine?
Par le protéasome.
What is the role of chromatin condensation?
The state of chromatin condensation regulates gene expression by making DNA more or less accessible to the transcription machinery.
What is an epigenetic modification?
An epigenetic modification is a chemical change that does not affect the DNA sequence but influences the state of chromatin condensation and DNA accessibility.
What is histone acetylation?
Histone acetylation increases DNA accessibility by adding an acetyl group to lysines in the histone tails, neutralizing their positive charge and reducing the interaction between histones and DNA.
What is the effect of histone acetylation on chromatin structure?
Histone acetylation causes a relaxation of chromatin structure, making DNA accessible to transcription enzymes and factors.
What is CpG island methylation?
Methylation of CpG islands prevents transcription factor binding by directly blocking their access or indirectly recruiting proteins that inhibit their binding.
Which base is methylated in human DNA?
Cytosine is the only base that can be methylated in human DNA, specifically when it forms a CpG dinucleotide with guanine.
What happens when CpG islands are methylated?
Methylation of CpG islands can lead to the recruitment of histone deacetylases, which modify histones and can ultimately increase transcription levels.
What is the relationship between histone acetylation and transcription levels?
Both histone acetylation and CpG island methylation can ultimately increase transcription levels.
What are the two types of transcription factors?
The two types of transcription factors are general transcription factors and specific transcription factors.
What is the role of general transcription factors?
General transcription factors are responsible for the recruitment of RNA polymerase II and the assembly of the transcription initiation complex.
What is the sequence associated with general transcription factors?
The sequence associated with general transcription factors is the promoter.
What is the efficiency of transcription initiation by general transcription factors?
The initiation of transcription by general transcription factors is effective but not very efficient.
What is the role of specific transcription factors?
Specific transcription factors control the level of transcription and are responsible for the expression of specific genes.
What sequences do specific transcription factors interact with?
Specific transcription factors interact with proximal, distal, or intronic regulatory sequences.
What types of proteins are specific transcription factors?
Specific transcription factors can be regulatory proteins such as activators or inhibitors.
How are specific transcription factors activated?
Specific transcription factors are induced or activated by extracellular signals.
What are the two types of distal regulatory sequences?
The two types of distal regulatory sequences are enhancers (amplifiers) and silencers (repressors).
How do specific transcription factors interact with the transcription complex?
Specific transcription factors can act on sequences adjacent to the promoter (proximal) and/or distant (distal) due to DNA folding that brings them into contact with the transcription complex.
What is the difference between repressors in prokaryotes and eukaryotes?
In prokaryotes, repressors bind to a DNA sequence called the operator, while in eukaryotes, they bind to DNA sequences.
What is required for basic transcription?
For basic transcription, general transcription factors are needed, and the promoter is sufficient.
What are enhancers?
Enhancers are regions that allow for high-level transcription by binding specific transcription factors called activators.
Where are enhancers located?
Enhancers can be located upstream, downstream, or within an intron of the gene’s promoter.
Do enhancers depend on their position and orientation?
No, enhancers function independently of their position and orientation.
Can a gene have multiple enhancers?
Yes, a gene can possess multiple enhancers of different specificities that can cooperate.
What is the role of activators in transcription initiation?
Activators facilitate the assembly of the transcription initiation complex.
What are the steps involved in the assembly of the transcription initiation complex?
1) Specific transcription factors (activators) bind to enhancers.
2) Proteins induce DNA bending through an ATP-dependent process.
3) Interactions between proteins facilitate the assembly and correct positioning of the initiation complex on the promoter.
What do activators bind to in the DNA?
Activators bind to control elements in the form of amplifiers in the DNA.
What is the role of the protein responsible for DNA bending?
The protein ensures that the bound activators are brought close to the promoter.
What proteins are located near the promoter?
General transcription factors, mediator proteins, and RNA polymerase are located near the promoter.
How do activators assist in transcription initiation?
Activators bind to mediator proteins and transcription factors to form an active transcription initiation complex that binds to the promoter.
What is the significance of intracellular receptors (R) in transcription?
Activated intracellular receptors act as specific transcription factors either directly or indirectly via mediator proteins.
Is the formation of a DNA loop for transcription activation common in prokaryotes or eukaryotes?
The activation of transcription by the formation of a DNA loop is rare in prokaryotes but common in eukaryotes.
What is a silencer?
A silencer is a DNA sequence that binds a specific transcription factor, inhibiting transcription generally independent of cell type.
Where is a silencer located?
A silencer can be located distantly from the gene promoter or within an intron.
How do silencers function?
Silencers function independently of their position and orientation.
What is the general function of a silencer in a gene?
A gene generally contains a silencer that works independently of cell type.
What are the ways inhibitors act?
Inhibitors act in several ways:
1) Competing for DNA binding.
2) Masking the activation surface.
3) Direct interactions with general transcription factors.
What is the first way an inhibitor acts?
The first way is by competing for DNA binding, preventing the binding of the activator.
What is the second way an inhibitor acts?
The second way is by masking the activation surface, preventing interaction with transcription factors via mediator proteins.
What is the third way an inhibitor acts?
The third way is through direct interactions with general transcription factors, excluding the activator and rendering the initiation complex assembly ineffective.
How is gene expression regulated?
Gene expression is regulated by several different regulatory sequences.
What ensures the specificity of gene expression?
The specificity of gene expression is ensured by the combination of specific transcription factors available in the cell.
What happens in a hepatic cell regarding albumin and crystalline genes?
In a hepatic cell, the albumin gene is expressed while the crystalline gene is not.
What happens in a crystalline cell regarding albumin and crystalline genes?
In a crystalline cell, the crystalline gene is expressed while the albumin gene is not.
