DNA is a special part of the cell. Without DNA, there would not have been life, evolution, survival, and existence. The base of synthesizing RNA starts from a DNA strand. Hence, DNA has a strict impact on the processes occurring in the body. DNA gets transcribed into RNA. Studying transcription helps to investigate how mutations affecting transcription cause inherited diseases. The first step involved in gene expression is transcription. Interested in cloning or treating a genetic disorder with DNA? Then keeping updates regarding transcription processes is helpful. RNA is a key nucleic acid involved in synthesizing proteins. Watson and Crick proposed the central dogma. It is a two-step process denoted as DNA leading to transcription of RNA and RNA leading to translation of the protein. Not all genes encode for proteins. Hence, not all DNA gets transcribed to RNA.





A gist of DNA replication:

Initiation of replication starts at a point where the unwinding of DNA takes place. Enzymes synthesize an RNA primer and the fragments so that new nucleotides get added. The segments get elongated through a process of elongation followed by removal of the primers. The unjoined fragments get ligated to end the process of replication. Using DNA as a template, the transcription starts.





RNA synthesis:

Genes are known as ordered sequences of nucleotide bases encoding polypeptide chains via RNA molecules. They are nothing but the pieces of DNA that consist of specific information for making a particular protein. Each gene associates with regulatory sequences known as gene regulatory elements. They are involved in regulation of transcription. The process of transcription starts with denaturation of the DNA double helix. The enzyme known as RNA polymerase catalyzes the process of transcription. In prokaryotes, RNA polymerase is responsible for unwinding. The process of unwinding in eukaryotes occurs with the help of other proteins. The DNA starts unwinding next to the gene involved the process. Hence, RNA polymerase starts catalyzing the RNA synthesis. The RNA gets synthesized from 5’-3’ direction along the 3’-5’ template strand. Out of the two DNA strands, only one strand participates in the process of transcription. Total four nucleotide phosphates act as precursors for transcription. They include ATP, GTP, CTP, and UTP. Recall that DNA synthesis requires RNA primers. However, RNA synthesis does not require primers. RNA polymerases are efficient in initiating the synthesis of new polynucleotide chains without any primers. Participant molecules in RNA synthesis are DNA strand, RNA polymerases, nucleoside triphosphates, elongation and termination factors. Also, there is a requirement of specific gene sequences for the initiation of transcription. In both prokaryotes and eukaryotes, the process of transcription occurs in three consecutive steps such as initiation, elongation, and termination. The eukaryotic transcription needs an understanding of prokaryotic transcription first.

A prokaryotic gene responsible for transcription needs the three following sequences:

· The promoter sequence is an upstream sequence present at the start of the RNA coding gene sequences.

· RNA coding gene sequences are known as DNA sequences capable of getting transcribed to RNA.

· The terminator specifies the destination point of transcription.

The genes specifying the initiation process have two promoter sequences known as -35 and -10. Each promoter has a specific consensus sequence.





Promoter region No. of base pairs upstream Consensus sequence -35 35 5’-TTGACA-3’ -10 10 5’-TATAAT-3’

Table: Promoters -35 and -10 respectively.