An Alternate History of DNA
LET'S TAKE a moment to explore a parallel universe, an alternate history. One in which a simple twist of fate has seriously altered the course of science.
This speculative journey comes courtesy of Matthew Cobb, a Professor of Zoology at the University of Manchester. A keen student of the past, Cobb recently explored the history of genetics and stumbled upon a consequential turning point concerning our knowledge of DNA. He weaved his discovery into an intriguing story in a recent issue of PLoS Biology.
DEOXYRIBONUCLEIC ACID (DNA) is the hereditary material in almost all organisms. The arrangement of its four bases – adenine (A), guanine (G), cytosine (C), and thymine (T) – constitutes the genetic code that tells life how to build itself. DNA is what makes you... you.
We know this thanks to a lengthy chain reaction of scientific discoveries. And according to Cobb, if there was a single man who catalyzed this reaction, it was Oswald Avery. In 1944, Avery, a medical researcher at Rockefeller University, published a paper with his colleagues Colin MacLeod and Maclyn McCarty. The experiment they described showed that DNA carries genetic information. While that seems obvious today, back then it was a controversial conclusion, countering decades of entrenched thought. DNA had originally been discovered back in 1869, but the majority of scientists considered it to be too simple to carry meaningful biological information. That duty, they assumed, belonged to proteins.
But a decade before Avery dented that dogma, he underwent surgery for Graves' disease. He survived, of course... but what if he didn't? Here is where Cobb's story begins.
"In an alternate reality, something went wrong on the operating table, and Avery died. His laboratory was closed, neither McCarty nor McLeod carried out their analytical work, and the transforming principle was not identified as DNA."
What would have happened? Cobb entertains a few possibilities.
IN THE FIRST possible timeline, history wouldn't change much at all. Avery's passing might have inspired his younger brother Roy, then a microbiologist at Vanderbilt, to take up his work. But for a slight change of names, history would remain relatively unaltered.
A second possibility sets the pace of science back substantially. DNA's role in heritability might not have been realized until Franklin, Watson, and Crick discovered the double helix structure of DNA in 1953. However, Cobb suggests that without Avery's foundational research, this finding might not have been enough to overturn conventional wisdom.
"In a world dominated by the idea that genes were made of proteins, the discovery of the double helix, and of complementary base-pairing, would not necessarily have led to the realisation that the DNA molecule can encode genetic information."
In this version of history, the discovery of DNA's double helix might merely have been academic, rather than revolutionary.
Regardless, Cobb's third possible timeline recognizes that "there was no single moment when scientists realised that genes were made of DNA." Through a gradual recognition of reality wrought from rigorous and skeptical experimentation, the scientific community would have accepted DNA's pivotal role.
"In 1950, Daniel Mazia highlighted two key experimental criteria that any substance thought to be the physical basis of the gene would have to meet: there had to be the same amount of the substance in every diploid cell of a given species and that amount had to double in mitosis and be halved during meiosis... it was obvious that no protein or group of proteins met these criteria."
Some iconoclast would have eventually challenged the scientific establishment, Cobb insists. And his or her ideas, when tested, would have won out.
"Because the genetic role of DNA is knowable and of intrinsic interest, had Avery not lived to carry out his work, someone else would inevitably have discovered that genes are made of DNA. "
Source: Cobb M (2016) A Speculative History of DNA: What If Oswald Avery Had Died in 1934? PLoS Biol 14(12): e2001197. doi:10.1371/journal.pbio.2001197