DNA Transcription

Transcription usually means the hereditary information stored in double-stranded DNA is duplicated or published in the kind of a single-stranded RNA molecule such as mRNA, tRNA, rRNA.  The first phase of the transfer of information from DNA into polypeptide is the transcription of a DNA nucleotide sequence to some RNA nucleotide sequence. 


After the conversion of DNA genetic information of each person (genotype) into the proteins, then a person's distinctive characters (phenotype) are shown.  Hence, the conversion of DNA to an RNA product is the first step of this transformation of data from DNA to Protein.

Steps involved in transcription:
In transcription, there are 3 Fundamental steps: initiation, elongation, and termination, which happens in both eukaryotes and prokaryotes. Even though the general procedure for transcription is quite similar in prokaryotes and eukaryotes, there are also some substantial differences. Transcription is initiated from the Promoter area, which is firstly bound by link proteins in both bacteria and eukaryotes.

Promoter: Promoter that serves as the control point in initiation of transcription is the element of specific DNA sequences recognized by transcription factor proteins. All these Promoter sequences direct RNA polymerase into the coding region of this gene and commences the purpose of the RNA polymerase.

Eukaryotic Promoters: All these promoters usually go toward 5' of the gene and have different elements that are distant from the transcription start site. Many eukaryotic promoters have a TATA box (This TATA box combines protein that helps create the RNA polymerase transcriptional complex and is located in close proximity to the transcription start site).

Prokaryotic Promoters: Transcription is initiated from the Promoter area, which is firstly bound by link proteins in both bacteria and eukaryotes. The promoters of All prokaryotes are constituted of two short sequences in the transcriptional start site that is located upstream at -10 and -35 bp (base pairs). The sequence at position -10 is named Pribnow box or the element of -10. This sequence generally includes 6 nucleotides as TATAAT. Pribnow box is needed for the initiation of transcription in prokaryotes. The other sequence at stake -35, is mostly composed of six nucleotides comprising TTGACA. The existence of this -35 sequence position guarantees a higher speed of transcription.


Initiation: RNA polymerase enzyme is responsible for RNA transcription. This enzyme is linked to particular components called as Promoters in DNA to begin RNA synthesis. 
Elongation: RNA polymerase enzyme synthesizes the RNA strand along the DNA chain. While the acting catalyst opens the front of double-stranded DNA, it generates the helical structure after the reaction. 
Termination: RNA synthesis continues along the DNA strand until it encounters the termination signal of this polymerase enzyme.

 Classification of RNA:
RNA is usually divided into two classes. 1 class of RNAs mediates gene decoding procedure for the polypeptide chain. These 'informative' RNAs are known as messenger RNAs (mRNAs).  All these RNAs transmit hereditary information in DNA to the ribosome. For the remaining genes in the minority, the RNA itself is the most significant operational product. This type of RNA is functional RNA.

The Messenger RNA (mRNA):
They are the RNAs which mediate the translation of genetic information in DNA to protein. They are protein-coding RNAs.

 Functional RNA (fRNA):
 These RNAs' genes, which are also called non-coding RNAs, create the functional RNA molecules instead of encoding proteins.

Transfer RNA (tRNA):
It is responsible for carrying amino acid toward mRNA in the process of translation. All types of tRNA are attached to a single sort of amino acid (20 amino acids are present in general) and carry it to the ribosome.

 Ribosomal RNA (rRNAs):
They are essential components of ribosomes. They guide gathering of amino acid string which is created by mRNA and tRNA with pretending to be large macromolecular machines.

Small nucleolar RNA (snoRNAs):
 Until 1995, more than 20 small nucleolar RNAs were detected. Small nucleolar RNAs are responsible for making various modifications after transcription for rRNA, tRNA, or small nuclear RNAs.
MicroRNA (miRNA):
 MicroRNAs are stored at a high degree, encoded from DNA areas but are translated to protein, are all approximately 18-24 nucleotides in length.  The miRNAs, execute the regulation of gene expression following transcription binding to the target mRNA that is complementary to its nucleotide sequences and contributes to translational inhibition or mRNA degradation. In this way, miRNAs play an essential role in homeostatic processes like cell proliferation, cell differentiation, and cell death.

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