GENETICS

DNA Carries the Message

1944 to 1952 CE

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

Something extracted from dead bacteria could permanently change the type of living ones, and after years of purification the something turned out to be DNA. Almost nobody believed it: proteins were varied and interesting, DNA was four units repeated, and a monotonous molecule seemed a poor place to keep a message. Eight years later, radioactive labels showed a virus injecting its DNA into a cell and leaving its protein coat outside.

Why it matters

Getting this wrong would have aimed the next fifty years of biology at the wrong molecule. It is also a lesson in what an argument from plausibility is worth: DNA looked too simple to carry information, and the reason it looked simple is precisely the reason it can be copied.

Dating & uncertainty

The 1944 transformation experiment was widely doubted, protein being the expected carrier. The 1952 phage experiment, which followed the DNA and the protein coat separately, ended the argument.

Sources

1. Avery, MacLeod & McCarty (1944), Journal of Experimental Medicine · Studies on the chemical nature of the substance inducing transformation of pneumococcal types
2. Hershey & Chase (1952), Journal of General Physiology · Independent functions of viral protein and nucleic acid in growth of bacteriophage

Earth history as one day

23:59:59.99841.6 ms before midnight

if Earth’s 4.54 billion years were compressed into a single day