Messenger RNA (mRNA) carries genetic information that directs protein synthesis
The concept of messenger RNA emerged during the late 1950s, and is associated with Crick's description of his "Central Dogma of Molecular Biology", which asserted that DNA led to the formation of RNA, which in turn led to the synthesis of proteins.During the early 1960s, sophisticated genetic analysis of mutations in the lac operon of E. coli and in the rII locus of bacteriophage T4were instrumental in defining the nature of both messenger RNA and the genetic code. The short-lived nature of bacterial RNAs, together with the highly complex nature of the cellular mRNA population, made the biochemical isolation of mRNA very challenging. This problem was overcome in the 1960s by the use of reticulocytes in vertebrates,[7] which produce large quantities of mRNA that are highly enriched in RNA encoding alpha- and beta-globin (the two major protein chains of hemoglobin).[8] The first direct experimental evidence for the existence of mRNA was provided by such a hemoglobin synthesizing system.[9]
https://en.wikipedia.org/wiki/History_of_RNA_biology