1961: S. Spiegelman demonstrates a hybrid molecule
containing ssDNA with an RNA complement opening
the way to the isolation of mRNA.
1965: S. Spiegelman, Haruna, Holland, Beaudreau, and
Mills demonstrate in vitro synthesis of
a self-propagating infectious RNA (bacteriophage
Qβ of E. coli) using purified
enzyme Qβ replicase.
1965: S. Spiegelman and Ritossa demonstrate that
mulitple cistrons producing ribosomal RNA of
Drosophila reside in the nucleolus
organizer regions of X and Y chromosomes.
1967: S. Spiegelman, Mills, and Peterson find a way to
select Qβ bacteriophage molecules that
replicate most rapidly in vitro. As
extracellular evolution progressed, the molecule
became smaller in proportion to the replication
rate increase. By the 74th transfer,
the RNA molecule (20% of its original length) was
the smallest known self-duplicating molecule.
1973: S. Spiegelman, Mills, and Kramer publish
the 218 replicating RNA nucleotide sequence (a
variant of Qβ phage).