In 1961, in the National Institutes of Health Headquarters (Bethesda, MD), Marshall Nirenberg and Heinrich Matthaei discovered the key to breaking the genetic code when they conducted an experiment using a synthetic RNA chain of multiple units of uracil to instruct a chain of amino acids to add phenylalanine. The uracil (poly-U) served as a messenger directing protein synthesis. This experiment demonstrated that messenger RNA transcribes genetic information from DNA, regulating the assembly of amino acids into complex proteins.
Genetic Code

YearAdded:
Image Credit: Courtesy Wikipedia/Infocan (CC BY-SA 3.0)Image Caption: Deciphering the Genetic CodeEra_date_from: 1961
1997