 Biochemists at the time were equally convinced that genes played an important role in protein synthesis (Judson 1979: Ch. 6 and 8; Morange 2020: Ch. 12; Rheinberger 1997). New evidence emerged from the medical genetics and biochemistry of sickle cell anemia, indicating the relation of gene mutations and amino acid alterations, from in vitro systems of protein synthesis based on e.coli cell extracts, leading to the characterization of ribosomes and transfer RNA (tRNA), as well as from work establishing the existence and role of messenger RNA (mRNA) and its complementarity to DNA. The image that resulted from this diverse evidence was that mRNA transferred information from nuclear DNA to the cytoplasm, where ribosomes, as largely unchanged structures, facilitated the assembly of amino acid chains based on the sequence of mRNA. In 1961, Crick and co-workers showed experimentally that three bases code for one amino acid, that coding triplets do not overlap and that they are read from a fixed starting point. In the same year, Marshall Nirenberg (1927–2010) and Heinrich Matthaei (born 1929) published results from an experiment in which synthetic RNA consisting only of uracil bases (RNA contains uracil, instead of thymine) was introduced in a cell free protein synthesis system, resulting in the production of a monotonous protein consisting of the amino acid Phenylalanine. Thus, it was shown that the RNA triplet UUU coded for this amino acid. This result opened the possibility to solve the genetic code experimentally and several labs participated in this project, leading to a complete table of correlated codons (coding triplets) and amino acids by 1967.