Barbara McClintock

From Wikiquote
Jump to navigation Jump to search
Barbara McClintock (1947)

Barbara McClintock (June 16, 1902 – September 2, 1992) was an American botanist and cytogeneticist. In 1983 she was awarded the Nobel Prize in Physiology or Medicine.


  • 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.
  • 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.

Quotes about McClintock[edit]

  • 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.

External links[edit]