Editing Barbara McClintock (section)

===Rediscovery===
McClintock officially retired from her position at the Carnegie Institution in 1967,{{sfn|Lamberts|2000}} and was made a Distinguished Service Member of the Carnegie Institution of Washington.{{sfn|Fedoroff|1995|p=221}} This honor allowed her to continue working with graduate students and colleagues in the Cold Spring Harbor Laboratory as ''scientist emerita''; she lived in the town.{{sfn|Kolata|1992}} In reference to her decision 20 years earlier to stop publishing detailed accounts of her work on controlling elements, she wrote in 1973:

{{blockquote|Over the years I have found that it is difficult if not impossible to bring to consciousness of another person the nature of his tacit assumptions when, by some special experiences, I have been made aware of them. This became painfully evident to me in my attempts during the 1950s to convince geneticists that the action of genes had to be and was controlled. It is now equally painful to recognize the fixity of assumptions that many persons hold on the nature of controlling elements in maize and the manners of their operation. One must await the right time for conceptual change.{{sfn|McClintock|1973}}}}

The importance of McClintock's contributions was revealed in the 1960s, when the work of French geneticists [[François Jacob]] and [[Jacques Monod]] described the genetic regulation of the [[lac operon|''lac'' operon]], a concept she had demonstrated with ''Ac/Ds'' in 1951. Following Jacob and Monod's 1961 ''Journal of Molecular Biology'' paper "Genetic regulatory mechanisms in the synthesis of proteins", McClintock wrote an article for ''[[American Naturalist]]'' comparing the ''lac'' operon and her work on controlling elements in maize.{{sfn|McClintock|1961|pp=265–277}}{{sfn|Fedoroff|1995|p=224}} Even late in the twentieth century, McClintock's contribution to biology was still not widely acknowledged as amounting to the discovery of genetic regulation.{{sfn|Comfort|1999|pp=133–162}} See Kass (2024, pp.&nbsp;189–191) for clarification of this legend.

McClintock was widely credited with discovering transposition after other researchers finally discovered the process in bacteria, yeast, and [[bacteriophage]]s in the late 1960s and early 1970s.{{sfn|Fedoroff|1995|p=213}} During this period, molecular biology had developed significant new technology, and scientists were able to show the molecular basis for transposition.{{sfn|Fedoroff|1995|p=227}} In the 1970s, ''Ac'' and ''Ds'' were [[cloning|cloned]] by other scientists and were shown to be [[transposon|class II transposons]]. ''Ac'' is a complete transposon that can produce a functional [[transposase]], which is required for the element to move within the genome. ''Ds'' has a mutation in its transposase gene, which means that it cannot move without another source of transposase. Thus, as McClintock observed, ''Ds'' cannot move in the absence of ''Ac''.<ref>{{cite journal |url=https://www.nature.com/scitable/topicpage/barbara-mcclintock-and-the-discovery-of-jumping-34083/|title=Barbara McClintock and the Discovery of Jumping Genes (Transposons)|last1=Pray |first1=Leslie |last2=Zhaurova |first2=Kira |journal=Nature Education |volume=1 |issue=1 |page=169}}</ref> ''Spm'' has also been characterized as a transposon. Subsequent research has shown that transposons typically do not move unless the cell is placed under stress, such as by irradiation or the breakage-fusion-bridge cycle, and thus their activation during stress can serve as a source of genetic variation for evolution.{{sfn|Pray|2008}} McClintock understood the role of transposons in evolution and genome change well before other researchers grasped the concept. Nowadays, ''Ac/Ds'' is used as a tool in plant biology to generate mutant plants used for the characterization of gene function.{{sfn|Jin|Duan|Zhang|Chen|2003}}