Barbara McClintock

"If chromosomes are broken by various means, the broken ends appear to be adhesive and tend to fuse with one another 2-by-2. This has been abundantly illustrated in the studies of chromosomal aberrations induced by X-ray treatment. It also occurs after mechanical rupture of ring-shaped chromosomes during somatic mitoses in maize and is assumed to occur during the normal process of crossing-over."

"When, through radiation or other causes, chromosomes are broken within a single nucleus, 2-by-2 fusions may occur between the broken ends. These fusions may lead to rearrangements of parts of the chromatin complement, giving rise to various chromosomal aberrations which are detected as reciprocal translocations, inversions, deficiencies, etc. Since, in the well-investigated cases, the breakages occurred within a single nucleus, the conditions that lead to fusions of broken ends could not easily be ascertained."

"An experiment conducted in the mid-nineteen forties prepared me to expect unusual responses of a genome to challenges for which the genome is unprepared to meet in an orderly, programmed manner. In most known instances of this kind, the types of response were not predictable in advance of initial observations of them. It was necessary to subject the genome repeatedly to the same challenge in order to observe and appreciate the nature of the changes it induces. Familiar examples of this are the production of mutation by X-rays and by some mutagenic agents. In contrast to such “shocks” for which the genome is unprepared, are those a genome must face repeatedly, and for which it is prepared to respond in a programmed manner. Examples are the “heat shock” responses in eukaryotic organisms, and the “SOS” responses in bacteria. Each of these initiates a highly programmed sequence of events within the cell that serves to cushion the effects of the shock. Some sensing mechanism must be present in these instances to alert the cell to imminent danger, and to set in motion the orderly sequence of events that will mitigate this danger. The responses of genomes to unanticipated challenges are not so precisely programmed. Nevertheless, these are sensed, and the genome responds in a descernible but initially unforeseen manner."

"In 1950, Barbara McClintock published a Classic PNAS article, “The origin and behavior of mutable loci in maize,” which summarized the evidence leading to her discovery of transposition. The article described a number of genome alterations revealed through her studies of the Dissociation locus, the first mobile genetic element she identified. McClintock described the suite of nuclear events, including transposon activation and various chromosome aberrations and rearrangements, that unfolded in the wake of genetic crosses that brought together two broken chromosomes 9. McClintock left future generations with the challenge of understanding how genomes respond to genetic and environmental stresses by mounting adaptive responses that frequently include genome restructuring."

"In the year of her election to the National Academy, she began the series of experiments that led her to transposition—work that many now see as the most important of her career. At the time, only she thought so. To most, her conclusions seemed too radical."

"When Barbara McClintock was awarded a Nobel Prize for her work on gene transposition in corn plants, the most striking thing about her was that she made her discoveries by listening to what the corn spoke to her, by respecting the life of the corn and "letting it McClintock says she learned "the stories" of the plants. She "heard them. She watched the daily green journeys of growth from carth toward sky and sun. She knew her plants in the way a healer or mystic would have known them, from the inside, the inner voices of corn and woman speaking to one another. As an Indian woman, I come from a long history of people who have listened to the language of this continent, people who have known that corn grows with the songs and prayers of the people, that it has a story to tell, that the world is alive...This intuitive and common language is what I seek for my writing, work in touch with the mystery and force of life, work that speaks a few of the many voices around us, and it is important to me that McClintock listened to the voices of corn. It is important to the continuance of life that she told the truth of her method and that it reminded us all of where our strength, our knowing, and our sustenance come from. It is also poetry, this science, and I note how often scientific theories lead to the world of poetry and vision, theories telling us how atoms that were stars have been transformed into our living, breathing bodies. And in these theories, or maybe they should be called stories, we begin to understand how we are each many people, including the stars we once were, and how we are in essence the earth and the universe, how what we do travels clear around the earth and returns. In a single moment of our living, there is our ancestral and personal history, our future, even our deaths planted in us and already growing toward their fulfillment. The corn plants are there, and like all the rest we are forever merging our borders with theirs in the world collective."