Name: rna types in gene expression
Uploaded: 2025-05-22T09:05:54.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

Georgia Standards of Excellence

9-12

Biology

SB2.a

Types of RNA

Il existe trois types d’ARN qui jouent un rôle direct dans la synthèse des protéines : l’ARN messager ou ARNm, l’ARN de transfert ou ARNt et l’ARN ribosomique ou ARNr.
L’ARNm est d’abord transcrit à partir de l’ADN par appariement de bases complémentaires. Dans une molécule d’ARNm, les codons, groupes de trois nucléotides, spécifient la séquence d’acides aminés et indiquent où la synthèse des protéines doit commencer et s’arrêter.
La traduction se produit après que l’ARNm se soit rendu dans le cytoplasme, où il est positionné sur la petite sous-unité ribosomique à l’aide de son ARNr.
Ensuite, une molécule d’ARNt, avec une séquence d’anticodon à trois nucléotides à une extrémité et un acide aminé spécifique à l’autre, se lie à un codon complémentaire dans l’ARNm.
Les ARNt corrects se lient à l’ARNm de manière séquentielle, et l’ARNr dans la grande sous-unité ribosomique catalyse la formation d’une liaison peptidique entre deux acides aminés.
Le ribosome descend le long de l’ARNm, créant un polypeptide avec une séquence d’acides aminés spécifiée par l’ARNm.

types d’arn

Trois principaux types d'ARN sont impliqués dans la synthèse des protéines : l'ARN messager (ARNm), l'ARN de transfert (ARNt) et l'ARN ribosomal (ARNr). Ces ARN remplissent diverses fonctions et peuvent être largement classés en ARN codants pour les protéines ou non codants. Les ARN non codants jouent un rôle important dans la régulation de l’expression des gènes en réponse aux changements développementaux et environnementaux. Les ARN non codants chez les procaryotes peuvent être manipulés pour développer des médicaments antibactériens plus efficaces à usage humain ou animal.

L'ARN Remplit des Fonctions Diverses mais Coopératives

Le dogme central de la biologie moléculaire déclare que l’ADN contient les informations qui codent pour les protéines et que l’ARN utilise ces informations pour diriger la synthèse des protéines.

L'ARN messager (ARNm) est l'ARN codant pour les protéines. Il se compose de codons, des séquences de trois nucléotides qui codent pour un acide aminé spécifique. L'ARN de transfert (ARNt) et l'ARN ribosomal (ARNr) sont des ARN non codants. L'ARNt agit comme une molécule adaptatrice qui lit la séquence d'ARNm et place les acides aminés dans le bon ordre dans la chaîne polypeptidique en croissance. L'ARNr et d'autres protéines constituent le ribosome, siège de la synthèse des protéines dans la cellule. Pendant la traduction, les ribosomes se déplacent le long d’un brin d’ARNm où ils stabilisent la liaison des molécules d’ARNt et catalysent la formation de liaisons peptidiques entre les acides aminés. Ainsi, différents types d’ARN remplissent des fonctions spécifiques mais complémentaires lors de la synthèse des protéines.

Les ARN Non Codants Chez les Eucaryotes Régulent l’Expression des Gènes

Les ARN non codants autres que l’ARNt et l’ARNr étaient initialement considérés comme des « déchets génomiques » car ils ne codent pas pour les protéines. Cependant, leur rôle dans la régulation de l’expression des gènes a été découvert au cours des dernières décennies et continue de faire l’objet de recherches approfondies. En fonction de leur longueur, les ARN non codants peuvent être classés en petits ARN régulateurs (< 100 nucléotides) ou en ARN longs non codants (> 200 nucléotides).

Les petits ARN régulateurs et les longs ARN non codants régulent l’expression des gènes en modifiant diverses étapes de transcription et de traduction. Les ARN non codants affectent l’épissage de l’ARNm : suppression des segments non codants et jonction des séquences codantes pour les protéines. De cette manière, ils contrôlent la formation de différentes variantes protéiques à partir d’un seul gène. Les petits ARN régulateurs tels que les microARN (miARN) et les petits ARN interférents (siARN) se lient aux séquences complémentaires de l'ARNm et inhibent la synthèse des protéines soit en bloquant l'accès de la machinerie de traduction à l'ARNm, soit en dégradant l'ARNm lui-même. Les longs ARN non codants interagissent avec et recrutent des enzymes qui modifient chimiquement l’ADN et les histones – des protéines qui aident à emballer l’ADN dans le noyau – pour activer ou réprimer la transcription.

Types d’ARN

Trois principaux types d’ARN sont impliqués dans la synthèse des protéines : l’ARN messager (ARNm), l’ARN de transfert (ARNt) et l’ARN ribosomique (ARNr). Ces ARN effectuent divers ...

Education

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Anatomie et physiologie

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Unité 1

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rna types in gene expression

RNA types play different roles in gene expression. RNA, or ribonucleic acid, helps carry and use genetic information in cells. The main types discussed here are messenger RNA, ribosomal RNA, and transfer RNA.

Messenger RNA, or mRNA, carries the genetic code from DNA to the ribosome. The ribosome is the site where proteins are made. Ribosomal RNA, or rRNA, is a key part of the ribosome itself. Transfer RNA, or tRNA, brings the correct amino acids to the ribosome during protein building.

These RNA molecules work together during protein synthesis. mRNA provides the message, rRNA helps form the protein-making machinery, and tRNA matches amino acids to the code. Understanding these RNA types helps explain how cells turn genetic instructions into proteins.

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Explore messenger RNA, ribosomal RNA, and transfer RNA, and see how each RNA type helps carry and use genetic information during protein synthesis.

RNA Types in Gene Expression | JoVE K12

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RNA Types in Gene Expression

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