Central Dogma of Biology

For Conversational Biology series – topic POLS

To learn a topic, it is nice to have a central framework upon which to build your “mind map”.  When it comes to biology, my central framework is called “The Central Dogma of Biology”.  To get us started learning about biology, I think it is appropriate to provide this concept for you to use when building your mind map of biology.

If we go back in time to 1956, we would find that Francis Crick was an important figure in biology, particularly molecular biology.  Just a few years earlier, he had looked at Rosalind Franklin’s data and, along with James Watson, had described the structure of deoxyribonucleic acid (DNA).  This was a big deal because biologist were beginning to come to grips with the idea that DNA is the molecule (a type of macromolecule under the umbrella of “nucleic acids”) that stores genetic information.  Prior to this, protein was the top dog in the minds of most scientists.  DNA was considered “boring” and proteins (another type of macromolecule) were considered to be more interesting, so it stood to reason that proteins would have been suspected to be the storage molecule for molecular biology. 

Anyway, back to the central dogma of biology (aka the central dogma of molecular biology).  This concept was proposed by Francis Crick.  His framework can be overly simplified to “DNA is transcribed to RNA and RNA is translated to protein” or, even more simply, “DNA à RNA à protein”, where the arrows are steps that read information of one molecule to create the next molecule in the progression.

Let’s back up a step again.  What’s RNA?  It, like DNA, belongs to the nucleic acid macromolecule class.  It looks a lot like DNA, but it is one oxygen molecule short, so RNA (ribonucleic acid) has a similar name to DNA (deoxyribonucleic acid).  Notice that the difference in the names is “deoxy”, which is a scientific way of saying “lacks an oxygen”.

Francis Crick had one more arrow in his “DNA à RNA à protein” framework and that was a reverse arrow between DNA and RNA (DNA ß RNA).  This left open the possibility that information in the form of RNA could be used to create a new molecule of DNA.  This turns out to be true, so this process is called “reverse transcription” since the process of DNA à RNA is called transcription.

One final point, Crick wisely avoided drawing an arrow from protein back to RNA (RNA ß protein).  When we get to the topic of the genetic code, we will see why “reverse translation” isn’t a thing.

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