What is transcription and explain the process
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Transcription is a mechanism for "recopying" gene data, enabling them to be used to create biological material by assembling amino acids into proteins according to the genetic code.
It takes place in the nucleus of a cell (in eukaryotes) and consists in copying so-called coding regions of the DNA and transcribing them into RNA molecules. Indeed, if the DNA molecule is the universal support for genetic information, it is the messenger RNA molecules that are recognized by the translation mechanism into protein sequences. Through messenger RNA, the cell can express the genetic information contained in its genes and manufacture the proteins necessary for its functioning.
The enzyme that catalyzes this transcription reaction is called RNA polymerase. There are several types in eukaryotes, involved in the transcription of several types of RNA (messenger, ribosomal, transfer, etc.) but only one type in prokaryotes. For example, in eukaryotes, it is RNA polymerase II that is responsible for transcribing DNA into pre-messenger RNA, while RNA polymerase I allows the synthesis of ribosomal RNA and RNA polymerase III (TRNA), small RNAs (such as pRNA or pRNA) and 5S ribosomal RNA (5S rRNA) are involved in the synthesis of short RNAs such as transfer RNA (tRNA). In prokaryotes, RNA polymerases allow the synthesis of all types of RNA.
During transcription, the helicase will separate the deoxyribonucleic acid (DNA) thus enabling the RNA polymerase to transcribe which initially recognizes and binds to a particular region of the DNA, located upstream of a coding region of DNA, A gene: the promoter site. This step will be described in more detail during the description of the initiation, first step of the transcription.
After transcription, the maturation of RNA (or post-transcriptional modification) and translation, the other two important steps in the biosynthesis of proteins. In the case of prokaryotes, on the other hand, no maturation is necessary before translation.
During RNA maturation, the RNA molecule directly synthesized from the DNA template (pre-messenger RNA) is supplemented by a tail (polyadenylation) and a 5 'end comprising several chemical modifications: the cap. The primary transcript of the messenger RNA remains in the nucleus and is subsequently treated with an enzymatic complex. This mechanism is called splicing: some sequences called introns are excised, and the remaining parts (exons) link together. For the same DNA transcript, identical pre-messenger RNAs may however undergo different splicing, then coding for different proteins. This phenomenon is called alternative splicing and makes it possible to increase the number of possibilities of mature messenger RNA, and thus of the proteins produced.
It takes place in the nucleus of a cell (in eukaryotes) and consists in copying so-called coding regions of the DNA and transcribing them into RNA molecules. Indeed, if the DNA molecule is the universal support for genetic information, it is the messenger RNA molecules that are recognized by the translation mechanism into protein sequences. Through messenger RNA, the cell can express the genetic information contained in its genes and manufacture the proteins necessary for its functioning.
The enzyme that catalyzes this transcription reaction is called RNA polymerase. There are several types in eukaryotes, involved in the transcription of several types of RNA (messenger, ribosomal, transfer, etc.) but only one type in prokaryotes. For example, in eukaryotes, it is RNA polymerase II that is responsible for transcribing DNA into pre-messenger RNA, while RNA polymerase I allows the synthesis of ribosomal RNA and RNA polymerase III (TRNA), small RNAs (such as pRNA or pRNA) and 5S ribosomal RNA (5S rRNA) are involved in the synthesis of short RNAs such as transfer RNA (tRNA). In prokaryotes, RNA polymerases allow the synthesis of all types of RNA.
During transcription, the helicase will separate the deoxyribonucleic acid (DNA) thus enabling the RNA polymerase to transcribe which initially recognizes and binds to a particular region of the DNA, located upstream of a coding region of DNA, A gene: the promoter site. This step will be described in more detail during the description of the initiation, first step of the transcription.
After transcription, the maturation of RNA (or post-transcriptional modification) and translation, the other two important steps in the biosynthesis of proteins. In the case of prokaryotes, on the other hand, no maturation is necessary before translation.
During RNA maturation, the RNA molecule directly synthesized from the DNA template (pre-messenger RNA) is supplemented by a tail (polyadenylation) and a 5 'end comprising several chemical modifications: the cap. The primary transcript of the messenger RNA remains in the nucleus and is subsequently treated with an enzymatic complex. This mechanism is called splicing: some sequences called introns are excised, and the remaining parts (exons) link together. For the same DNA transcript, identical pre-messenger RNAs may however undergo different splicing, then coding for different proteins. This phenomenon is called alternative splicing and makes it possible to increase the number of possibilities of mature messenger RNA, and thus of the proteins produced.
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Transcription is the synthesis of an RNA strand from a DNA template. A gene's protein building instructions are transcribed to messenger RNA (mRNA). mRNA carries the code from DNA to the ribosomes where translation into a protein occurs.
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