Central Dogma
மத்திய கோட்பாடு
Do not mistake the Central Dogma for a simple linear path. Francis Crick proposed this unidirectional flow, but retroviruses like HIV violate this rule by using Reverse Transcriptase. If you ignore the exceptions, you lose the rank.
The idea
The Central Dogma describes the unidirectional flow of genetic information: DNA to RNA via transcription, and RNA to protein via translation. DNA acts as the master template, mRNA serves as the messenger, and ribosomes facilitate polypeptide synthesis. This process is the fundamental mechanism of gene expression in all living organisms.
Why it matters
This flow ensures that the information stored in the stable DNA molecule is converted into functional proteins that perform cellular activities.
NEET lens
NEET focuses on the directionality and the exceptions. Memorize that Reverse Transcription is the primary exception to Crick's dogma. Expect questions matching processes to their respective enzymes: RNA Polymerase for transcription and Ribosomes for translation. Do not confuse the template strand with the coding strand.
Clinical significance
When this flow is disrupted, cellular homeostasis collapses. Mutations in DNA lead to faulty mRNA, resulting in non-functional proteins, which is the root cause of genetic disorders like Sickle Cell Anemia. In viral infections, the host machinery is hijacked to prioritize viral protein synthesis over cellular needs.
Introduction
The central dogma, proposed by Francis Crick, states that genetic information flows from DNA → RNA → protein.
Core concept
Steps: replication (DNA → DNA), transcription (DNA → RNA), translation (RNA → protein). Exception: in some viruses (retroviruses such as HIV) the flow is reversed from RNA to DNA by the enzyme reverse transcriptase. Types of RNA in bacteria: mRNA provides the template, tRNA brings amino acids and reads the code, rRNA plays structural and catalytic roles during translation.
Go deeper
RNA was probably the first genetic material (RNA world): it can store information and act as a catalyst. DNA, being more stable, evolved later as the main store of information.
From Class 10
Think of DNA as the master copy locked in a library, RNA as the photocopy taken out, and protein as the finished product made from it.