Questions and Assays

Abstract

The Thomas Hunt Morgan Medal is awarded to an individual Genetics Society of America member for lifetime achievement in the field of genetics. It recognizes the full body of work of an exceptional geneticist. The 2016 recipient is Nancy Kleckner, who has made many significant contributions to our understanding of chromosomes and the mechanisms of inheritance. Kleckner has made seminal achievements in several different research areas, including bacterial transposition, chromosome organization, and meiosis. She has repeatedly combined traditional genetic approaches with molecular biology, microscopy, physics, and modeling—unprecedented applications of these methods at the time, but which have now become commonplace. Indeed, she is widely recognized as one of the leaders in bringing meiosis research into the modern era. Notably, her laboratory played a key role in elucidating the mechanism that initiates meiotic recombination, has helped to decipher the “strand gymnastics” of recombination, and is beginning to provide insight into the enigmatic phenomenon of crossover interference.

Paranemic Crossover DNA: There and Back Again

“…As illustrated in Figure , this fusion is believed to be activated by Gibbs free energy (associated with supercoiled DNA in prokaryotes, as circular plasmids, and in eukaryotes, as packed around histones in chromatin) and driven by the relaxation of supercoiling via forming PX structure (the formation of PX-DNA can untwist B-DNA) in the presence of DNA homology. The observation agrees with the note that every functional output of DNA is shaped by mechanical properties conferred by DNA topology and supercoiling . Moreover, atomic force microscopic (AFM) imaging of the patterns generated in vitro and in vivo after psoralen cross-linking further proves that strands in the two homologous regions form DNA crossovers, like those formed in PX, rather than a bare DNA–DNA backbone juxtaposition .…”

“…The observation agrees with the note that every functional output of DNA is shaped by mechanical properties conferred by DNA topology and supercoiling. 88 Moreover, atomic force microscopic (AFM) imaging of the patterns generated in vitro and in vivo after psoralen cross-linking further proves that strands in the two homologous regions form DNA crossovers, like those formed in PX, rather than a bare DNA−DNA backbone juxtaposition. 24 Departing from this point, more in vivo effort is needed to elucidate the biological functions of PX motif in RIHP.…”

Complex between a Multicrossover DNA Nanostructure, PX-DNA, and T7 Endonuclease I

“…This observation also agrees with the conclusion that every functional output of DNA is shaped by mechanical properties conferred by DNA topology and supercoiling. 45 Formation of shaftlike structure was first verified by two-dimensional (2D) gel electrophoresis, an established method used to demonstrate a structural transition from B-DNA to a noncanonical DNA structure, including H-form and Z-DNA, to relax the supercoiled plasmid; [46][47][48] the result excludes the possibility that the shaft structure resulted from a bare DNA-DNA juxtaposition, as predicted by an electrostatic model, because the formation of a regular B-form DNA juxtaposition cannot relax the supercoiled plasmid. Furthermore, AFM (atomic force microscopy) imaging results show that the shafts form in exact regions of the plasmids where PX or fullly homologous DNA segments were inserted.…”