Central Dogma of Molecular Biology

The Central Dogma of genetics explains how genetic information flows from DNA to RNA to proteins within living organisms. It is a framework that describes how genetic information flows within a biological system. The Central Dogma outlines the sequential steps through which genetic information is transferred within a cell. The Central Dogma of molecular biology was given by Francis Crick.

Central-Dogma-diagram

Steps of the Central Dogma

The Central Dogma of molecular biology is a concept that outlines the flow of genetic information within a biological system. The key steps in the Central Dogma are:

Replication: The process by which DNA makes an identical copy of itself, ensuring the transmission of genetic information to the next generation during cell division.
Transcription: The synthesis of RNA (specifically, messenger RNA or mRNA) from a DNA template. This step occurs in the cell nucleus and serves as a temporary copy of genetic information for protein synthesis.
Translation: The process in which the information encoded in mRNA is used to build a corresponding protein. This occurs at the ribosomes in the cell cytoplasm, where transfer RNA (tRNA) molecules bring amino acids to the ribosome, allowing the formation of a polypeptide chain.

Central Dogma - Replication

In this step, the DNA duplicates itself by ensuring that each daughter cell receives an identical copy of the genetic material. Here are some steps related to it, as mentioned below.

Steps of Replications	Description
1. Initiation	The replication process starts with the unwinding of the double helix DNA. Various enzymes, specifically DNA helicase, help in this process.
2. Elongation	DNA polymerase adds nucleotides to the single strands, which leads to the formation of two identical DNA strands. The process occurs in a 5' to 3' direction.
3. Termination	After the duplication process of the entire DNA module, the process of replication ends. After replication, each DNA module consists of one original strand of the previous DNA and one new synthesised strand.

Central Dogma - Transcription

Transcription is the synthesis process of mRNA from a DNA template. RNA polymerase binds to the DNA at the promoter region. After that, it synthesises a complementary RNA strand by adding nucleotides according to the base-pairing rules (A-U, C-G). Here are the steps as mentioned below.

Steps of Transcription	Description
1. Initiation	To set up the starting point of the transcription process, RNA polymerase binds to the promoter region (which controls the binding of RNA polymerase to DNA) of the DNA. At this stage, DNA strands unwind by exposing the template.
2. Elongation	By adding nucleotides, RNA polymerase synthesises another complementary RNA in the 5' to 3' direction. In this stage, RNA molecules grow and read the template DNA strand.
3. Termination	The step concludes when the RNA polymerase reaches the termination. At this point, the transcript of RNA is released, and DNA strands pair with each other in a double helix structure.

Central Dogma - Translation

Translation is the process by which the mRNA sequence is decoded to produce a specific protein. It occurs in the cytoplasm at ribosomes. The tRNA molecules bring amino acids to the ribosome according to the mRNA codons, and the amino acids are linked together to form a polypeptide chain. Here are the steps.

Steps of Translation	Description
1. Initiation	The mRNA molecules bind the ribosomal subunits. tRNA works as an initiator of the process by carrying the amino acids and pairing with the mRNA.
2. Elongation	In this step, successive tRNA molecules bring amino acids to the ribosome based on mRNA codons (DNA or RNA sequence of three nucleotides). The process creates peptide bonds between the adjacent amino acids to form the polypeptide chain.
3. Termination	When a stop codon reaches the mRNA, the process concludes. At this point, polypeptide chains get released from the ribosome.

Functions of DNA and RNA in the Central Dogma

Here we are going to discuss the functions of DNA and RNA in the central dogma, as mentioned below.

DNA

The core function of DNA is to store the genetic information.
In the process of replication, DNA works as a template to perform the synthesis of an identical copy.
DNA ensures that the genetic information is passed accurately during the cell division process to the next cell.
In the transcription stage, DNA works as a command centre to perform the process of protein synthesis.
In this stage, DNA works as a template to produce contemporary RNA.

RNA

In the translation stage, mRNA carries the genetic codes, tRNA carries the amino acids, and rRNA performs the process of protein synthesis by creating peptide bonds between amino acids.
In the transcription stage, RNA carries the instructions to the protein synthesis machinery encoded in DNA.

Modern Discoveries in Central Dogma

The following is the Modern Discoveries in the Central Dogma:

Process	Description	Discoveries
Replication	DNA makes an identical copy of itself.	-
Transcription	DNA is transcribed into mRNA.	Reverse transcription in retroviruses challenges unidirectionality.
Translation	mRNA is translated into a protein.	Non-coding RNAs, alternative splicing, and epigenetic regulation add complexity.

Genetic Code
Nucleotide vs Nucleoside
DNA vs RNA
Transcription of DNA
Protein Synthesis
DNA Replication