Season 1 Weekly

The Great Dictator

“All hail the Great DNA!”, shouted an army of microtubules from a prominent locus in the cytoplasm. “DNAaaaa, DNA!” clap clap clap “DNAaaaa, DNA!” shouted out all the organelles of the cell, from the juniors like glyoxysomes to the seniors like mitochondria, all alike. Although the envious RNAs looked on with inaudible grunts and disapproving growls, they too had to submit after a few minutes of cheerleading the Boss, the Great Dictator, DNA!

Unlike every other dictator DNA did not have its roots in desperation to overthrow the existing rule. It was a born hero. Ever since Deoxyribonucleic acid, who goes by the name of DNA among his followers, was synthesized in a primordial soup of nutrients few billion years ago, it had been widely accepted as the boss. Till today, no one else, has been able to overthrow its dominance.

In case you wonder, “Why?”, you should ask the historians of cytology, the introns, who are reminiscent of antiquity! They, though themselves made up of DNA, will tell you that DNA’s secret to dominance in genetic inheritance is due its stability. Lack of a hydroxyl group in the pentose sugar, unlike RNA, presence of methylation in nitrogen bases, i.e thymine of DNA instead of uracil of RNA, double stranded nature as compared to mostly single stranded RNA suffices for its ascension in the throne of cyto-dictator overthrowing the RNA rule. DNA also takes keen interest in self replication, having sequences to code for proteins, that synthesize two newer daughter DNAs from the parent one. It is not fickle minded like RNA, and undergoes mutation fairly stably, hence, the DNA which coded for peptidoglycan 3 Billion years ago, still codes for the same NAG NAM polymer today.

But, my intention to write today’s article, is to narrate the DNA’s dictation. It begins with transcription. A puzzle that DNA asks its subordinate RNA to solve. Often, while slithering through the great lengths of a DNA molecule, you will find a sequence that urges RNA factories to bind to the location. Following that promoter sequence which initiates the game, is the main puzzle that DNA asks RNA to solve. Like a dutiful servant, RNA factory aka RNA polymerase transcribes DNA’s blabbering code into a not-very-different RNA code. This new RNA has a fancy name: mRNA, m for messenger as all it does is transport the info to cytoplasm where other versatile RNAs wait hungrily to solve the code. Before the transportation though, mRNA likes to dress up, capped by an awkward N-base and tailed by an A obsessive tail! Also it undergoes dieting i.e. cutting away of any intervening transcribed historians aka introns, whom we met before. All this happens inside the nucleus.

Outside the comfort of nucleus wanders about millions of ribosomes. rRNAs who run each ribosome, like to call themselves protein factories. They allow the mRNA for a nights stay and read up their transcribed code, to steal amino acids from charged tRNAs and synthesize proteins! Quite hardworking, ain’t they? This is called translation. The language of RNA world is then translated into the language of proteins, with words called amino acids, that are understandable by every cell component.

It took humanity 11,953 years to decipher this process, since 10,000 BC, which was about 64 years before today. Though thanks for that usually goes to Watson, Crick, Wilkins and Chargaff, let us take this opportunity to thank Rosalind Franklin, who had probably the greatest contribution among them and yet the least recognition.

Before concluding, I want you to know that, this DNA is a bad guy. It has a closed community and 46 family members in human cells. They break up equally into two groups randomly, then associate with another such group of 23 from another human, and combines to dictate orders in a new cell, which we humans superficially term as birth of a new life!

P.S. This article was initially published in 2017.

Arkadeep Mukhopadhyay