DNA — The Discovery Story

For a very long time, Biologists considered proteins to be the bearer of genetic instructions from generation to generation. We all know proteins consist of 20 amino acids. Theoretically, the permutations of them could be infinite and hence was thought to encode life’s extraordinary diversity with ease. DNA on the other hand was never even considered as an ideal candidate for carrying the life’s magical code-scripts. This is a belief the world had.

Base of life…

Here is a fascinating story on how scientists accidentally discovered the truth behind DNA.

In 1928, Fred Griffith, a scientist in the British ministry of health was very interested in Pneumonia and its bacterial agent which was causing it.

There were two strains of this bacterial agent based on how they appear under the microscope. One was considered smooth(S) and the other Rough(R). (S) strains had a smooth protective coating on its surface which acted like the invisible cloak of Harry Potter. Magically, If injected, immune system of the host cannot recognise this invader and hence the host dies. Whereas the R strain is without the protective cover and hence when injected, the host’s immune system kills the bacterial agent and the host survives.

Griffith was curious to understand how these different strains interact with a mice. He injected a dead S Bacteria(Harmless) and also a live R bacteria(harmless) to a mice at the same time. According to his assumptions, the mouse should have survived. But, the Mouse Died…..

He was taken aback for a moment. He tried to retrieve the bacteria from the dead mouse and found that it was a living S bacteria. It looked like the R bacteria has acquired something from the dead S bacteria to become a living killer S bacteria. At that point in time, this transformation phenomenon was beyond ones understanding.

In 1944, 16 years later another scientist Oswald Avery was curious to understand what was happening in Griffith’s experiment. He set out to try the same experiment to find out what exactly was causing this transformation. He used a test tube and introduced the dead S strain and the live R strain.

Trial 1

He removed the protective coating in the Dead S strain bacteria. To his Amazement, transformation still happened.

Trial 2

As was believed by everyone, he tried to destroy all the proteins in the S Bacteria. His assumption was if he killed the proteins which carries the genetic information, the R strain would remain unaffected. To his surprise, it transformed again.

Trial 3

He destroyed the RNA from the Dead S Bacteria. The transformation still occurred.

Trial 4

Finally with no other option left, he introduced DNA destroying enzyme to the dead S bacteria. Astonishingly, the transformation ceased.

He along with MacLeod and McCarty released the results of this experiment as a paper in 1944. Unfortunately, this paper was received with mixed response since many biochemists raised doubts on whether DNA was complex enough to really hold such vast information. However, this marked the beginning of a new era of DNA. Because of this research, the whole biologists community was redirected in the right path from what was initially believed to be true.

This story fascinates us for few reasons. It shows that what we know of life today is incomplete. What we perceive as right today could be debunked as myth tomorrow. The real pleasure and satisfaction lies in getting to the core of the problem and solving it in the right way and not just follow course. Hence, it becomes important to not limit our imagination to what the world believes in today. Have an open mind, don’t be scared to start from scratch and let your thoughts fly far away from what the world believes in…