DNA Replication vs Transcription
 

These are highly complex and highly regulated processes take place at the cellular level. However, due to the complexity of the processes and the terms being unfamiliar, DNA replication and transcription are not popularly known. In fact, a substantial amount of people with backgrounds of biological science is not well aware of those terms. Therefore, this article aims to discuss the major events that take place during these processes and important distinctions of one over other briefly and a simplified manner.

What is DNA Replication?

DNA replication is the process of producing two identical DNA strands from one, and it involves a series of processes. All these processes take place during the S phase of the Inter-phase of cell cycle or cell division. It is an energy consuming process and primarily three main enzymes known as DNA helicase, DNA polymerase, and DNA ligase are involved in regulating this process. First, DNA helicase dismantles the double helix structure of the DNA strand by breaking the hydrogen bonds between the nitrogenous bases of the opposing strands. This dismantling starts from an end of the DNA strand and not from the middle. Therefore, DNA helicase could be regarded as a restriction exonuclease. After exposing the nitrogenous bases of the single-stranded DNA, the corresponding Deoxyribonucleotides are arranged according to the base sequence, and the respective hydrogen bonds are formed by DNA polymerase enzyme. This particular process takes place on both DNA strands. Finally, the phosphodiester bonds are formed between successive nucleotides, to complete the DNA strand using DNA ligase enzyme. At the end of all these steps, two identical DNA strands are formed from only one mother DNA strand.

What is DNA Transcription?

Transcription is a vital step of the main process of gene expression or protein synthesis. Primarily, the copying of the nitrogenous base sequence of part of a DNA strand into a messenger RNA takes place during DNA transcription. RNA polymerase enzyme breaks the hydrogen bonds at the desired place of the DNA strand and open double helix structure to expose the nitrogenous base sequence. RNA polymerase arranges the matching Ribonucleotides according to the exposed base sequence of the DNA strand. Furthermore, RNA polymerase enzyme aids in forming the new strand by forming the sugar-phosphate bonds. Since the newly formed strand consists of ribonucleotides, it is a RNA strand, and this strand gives the base sequence to the next step of the protein synthesis or gene expression. Therefore, it is referred as a messenger RNA strand (mRNA). However, after the sequencing of the nitrogenous bases, the sequence in mRNA is the same as in the DNA sequence, except for Thymine bases being replaced by Uracil base. At the end of transcription, a mRNA strand resembling the corresponding the gene of interest in the DNA strand is formed.

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