Cleavage of DNA by R1 restriction endonuclease generates cohesive ends.

Order of authorship in the original publication: Mertz, Davis. Mertz discovered that DNA ends generated by cutting with the EcoRI restriction enzyme are “sticky”, permitting any two such DNAs to be readily “recombined”. Using this discovery, in June 1972 "she easily created the first recombinant DNA that could have been cloned in bacteria. Her success with this project contributed to her thesis adviser, Paul Berg, receiving the 1980 Nobel Prize in Chemistry.^[16] However, Mertz did not proceed with this cloning because of the moratorium in place at that time, leaving it for Herbert Boyer, Stanley N. Cohen and their colleagues to prove in 1973 that recombinant DNAs made by this method can actually self-replicate in bacteria.^[17] (Wikipedia article on Janet E. Mertz, accessed 3-2020). Digital facsimile from PubMedCentral at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)