2 Réplication De L'Expression Génique

Question 1

Qu’est-ce que la différenciation chez l’homme?

Answer 1

La différenciation chez l’homme est irréversible; une fois une cellule spécialisée, elle perd la capacité d’assurer d’autres fonctions.

Question 2

Que signifie l’équivalence génomique?

Answer 2

Toutes les cellules d’un organisme pluricellulaire possèdent le même génome, mais elles n’expriment pas les mêmes gènes.

Question 3

Qu’est-ce que l’épissage alternatif?

Answer 3

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.

Question 4

Quel est le rôle du contrôle de l’expression génique?

Answer 4

Il permet à la cellule de modifier l’expression de ses gènes en réponse à un signal externe.

Question 5

Chez quels organismes a lieu l’expression génique?

Answer 5

L’expression génique n’a lieu que chez les eucaryotes.

Question 6

Qu’est-ce que la maturation de l’ARN?

Answer 6

La maturation de l’ARN inclut l’épissage alternatif.

Question 7

Qu’est-ce que la maturation de la protéine?

Answer 7

La maturation de la protéine inclut l’ubiquitination.

Question 8

Quels sont les 6 étapes de régulation de l’expression génique?

Answer 8

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.

Question 9

Quels facteurs influencent la structure de la chromatine?

Answer 9

Les modifications épigénétiques comme l’acétylation des histones et la méthylation des îlots CpG.

Question 10

Quels sont les éléments impliqués dans l’initiation de la transcription?

Answer 10

Les facteurs de transcription généraux et spécifiques.

Question 11

Comment la durée de vie de l’ARNm est-elle régulée?

Answer 11

Elle est régulée selon les 3’UTR et l’ARN interférence.

Question 12

Quel est le rôle de l’ARN interférence dans l’initiation de la traduction?

Answer 12

L’ARN interférence (miARN) et les protéines régulatrices influencent l’initiation de la traduction selon les 5’UTR ou 3’UTR.

Question 13

Comment se fait la dégradation de la protéine?

Answer 13

Par le protéasome.

Question 14

What is the role of chromatin condensation?

Answer 14

The state of chromatin condensation regulates gene expression by making DNA more or less accessible to the transcription machinery.

Question 15

What is an epigenetic modification?

Answer 15

An epigenetic modification is a chemical change that does not affect the DNA sequence but influences the state of chromatin condensation and DNA accessibility.

Question 16

What is histone acetylation?

Answer 16

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.

Question 17

What is the effect of histone acetylation on chromatin structure?

Answer 17

Histone acetylation causes a relaxation of chromatin structure, making DNA accessible to transcription enzymes and factors.

Question 18

What is CpG island methylation?

Answer 18

Methylation of CpG islands prevents transcription factor binding by directly blocking their access or indirectly recruiting proteins that inhibit their binding.

Question 19

Which base is methylated in human DNA?

Answer 19

Cytosine is the only base that can be methylated in human DNA, specifically when it forms a CpG dinucleotide with guanine.

Question 20

What happens when CpG islands are methylated?

Answer 20

Methylation of CpG islands can lead to the recruitment of histone deacetylases, which modify histones and can ultimately increase transcription levels.

Question 21

What is the relationship between histone acetylation and transcription levels?

Answer 21

Both histone acetylation and CpG island methylation can ultimately increase transcription levels.

Question 22

What are the two types of transcription factors?

Answer 22

The two types of transcription factors are general transcription factors and specific transcription factors.

Question 23

What is the role of general transcription factors?

Answer 23

General transcription factors are responsible for the recruitment of RNA polymerase II and the assembly of the transcription initiation complex.

Question 24

What is the sequence associated with general transcription factors?

Answer 24

The sequence associated with general transcription factors is the promoter.

Question 25

What is the efficiency of transcription initiation by general transcription factors?

Answer 25

The initiation of transcription by general transcription factors is effective but not very efficient.

Question 26

What is the role of specific transcription factors?

Answer 26

Specific transcription factors control the level of transcription and are responsible for the expression of specific genes.

Question 27

What sequences do specific transcription factors interact with?

Answer 27

Specific transcription factors interact with proximal, distal, or intronic regulatory sequences.

Question 28

What types of proteins are specific transcription factors?

Answer 28

Specific transcription factors can be regulatory proteins such as activators or inhibitors.

Question 29

How are specific transcription factors activated?

Answer 29

Specific transcription factors are induced or activated by extracellular signals.

Question 30

What are the two types of distal regulatory sequences?

Answer 30

The two types of distal regulatory sequences are enhancers (amplifiers) and silencers (repressors).

Question 31

How do specific transcription factors interact with the transcription complex?

Answer 31

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.

Question 32

What is the difference between repressors in prokaryotes and eukaryotes?

Answer 32

In prokaryotes, repressors bind to a DNA sequence called the operator, while in eukaryotes, they bind to DNA sequences.

Question 33

What is required for basic transcription?

Answer 33

For basic transcription, general transcription factors are needed, and the promoter is sufficient.

Question 34

What are enhancers?

Answer 34

Enhancers are regions that allow for high-level transcription by binding specific transcription factors called activators.

Question 35

Where are enhancers located?

Answer 35

Enhancers can be located upstream, downstream, or within an intron of the gene's promoter.

Question 36

Do enhancers depend on their position and orientation?

Answer 36

No, enhancers function independently of their position and orientation.

Question 37

Can a gene have multiple enhancers?

Answer 37

Yes, a gene can possess multiple enhancers of different specificities that can cooperate.

Question 38

What is the role of activators in transcription initiation?

Answer 38

Activators facilitate the assembly of the transcription initiation complex.

Question 39

What are the steps involved in the assembly of the transcription initiation complex?

Answer 39

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.

Question 40

What do activators bind to in the DNA?

Answer 40

Activators bind to control elements in the form of amplifiers in the DNA.

Question 41

What is the role of the protein responsible for DNA bending?

Answer 41

The protein ensures that the bound activators are brought close to the promoter.

Question 42

What proteins are located near the promoter?

Answer 42

General transcription factors, mediator proteins, and RNA polymerase are located near the promoter.

Question 43

How do activators assist in transcription initiation?

Answer 43

Activators bind to mediator proteins and transcription factors to form an active transcription initiation complex that binds to the promoter.

Question 44

What is the significance of intracellular receptors (R) in transcription?

Answer 44

Activated intracellular receptors act as specific transcription factors either directly or indirectly via mediator proteins.

Question 45

Is the formation of a DNA loop for transcription activation common in prokaryotes or eukaryotes?

Answer 45

The activation of transcription by the formation of a DNA loop is rare in prokaryotes but common in eukaryotes.

Question 46

What is a silencer?

Answer 46

A silencer is a DNA sequence that binds a specific transcription factor, inhibiting transcription generally independent of cell type.

Question 47

Where is a silencer located?

Answer 47

A silencer can be located distantly from the gene promoter or within an intron.

Question 48

How do silencers function?

Answer 48

Silencers function independently of their position and orientation.

Question 49

What is the general function of a silencer in a gene?

Answer 49

A gene generally contains a silencer that works independently of cell type.

Question 50

What are the ways inhibitors act?

Answer 50

Inhibitors act in several ways: 1) Competing for DNA binding. 2) Masking the activation surface. 3) Direct interactions with general transcription factors.

Question 51

What is the first way an inhibitor acts?

Answer 51

The first way is by competing for DNA binding, preventing the binding of the activator.

Question 52

What is the second way an inhibitor acts?

Answer 52

The second way is by masking the activation surface, preventing interaction with transcription factors via mediator proteins.

Question 53

What is the third way an inhibitor acts?

Answer 53

The third way is through direct interactions with general transcription factors, excluding the activator and rendering the initiation complex assembly ineffective.

Question 54

How is gene expression regulated?

Answer 54

Gene expression is regulated by several different regulatory sequences.

Question 55

What ensures the specificity of gene expression?

Answer 55

The specificity of gene expression is ensured by the combination of specific transcription factors available in the cell.

Question 56

What happens in a hepatic cell regarding albumin and crystalline genes?

Answer 56

In a hepatic cell, the albumin gene is expressed while the crystalline gene is not.

Question 57

What happens in a crystalline cell regarding albumin and crystalline genes?

Answer 57

In a crystalline cell, the crystalline gene is expressed while the albumin gene is not.