Barbara McClintock and Transposable Genetic Elements
Barbara McClintock's remarkable life spanned the history of genetics in the twentieth century. ... [T]he science of genetics, to which McClintock made seminal contributions both experimental and conceptual, has come to dominate all of the biological sciences, from molecular biology, through cell and developmental biology, to medicine and agriculture. ...
McClintock made her first significant contribution as a graduate student, developing cytological techniques that allowed her to identify each of the ten maize chromosomes. These early experiments laid the groundwork for a remarkable series of cytogenetic discoveries ... [for which] McClintock was the intellectual driving force ... . These include identification of maize linkage groups with individual chromosomes, the well-known cytological proof of genetic crossing-over, evidence of chromatid crossing-over, cytological determination of the physical location of genes within chromosomes, identification of the genetic consequences of nonhomologous pairing, establishment of the causal relationship between the instability of ring-shaped chromosomes and phenotypic variegation, discovery that the centromere is divisible, and identification of a chromosomal site essential for the formation of the nucleolus. ...
[McClintock was] interested in chromosome breakage, making important observations on the behavior of chromosomes lacking telomeres. ... These observations so intrigued her that she began an intensive investigation of the chromosome-breaking locus. Within several years she had learned enough to reach the conclusion, published in 1948, that the chromosome-breaking locus did something hitherto unknown for any genetic locus: it moved from one chromosomal location to another, a phenomenon she called transposition. The study of transposable genetic elements and transposition became the central theme of her genetic experiments from the mid-1940s until the end of her active research career. ...
[After meeting "McClintock, Fedoroff]" was prompted to read her papers from beginning to end ... [and] was intrigued with what [she] found to be a marvelous genetic detective story. ... [Their] relationship began in earnest ... during the summer of 1979 at the Brookhaven National Laboratory, where we ... [interacted with] Ben and Frances Burr. ...
By the time the maize elements were cloned and their molecular analysis began, the importance of McClintock's discovery of transposition was widely recognized. ... [I]n 1983, thirty-five years after publication of the first evidence for transposition, McClintock was awarded the Nobel Prize for Physiology or Medicine ["for her discovery of mobile genetic elements"] .
Additional information about Barbara McClintock and her research is available in full text and on the Web.
Movable Genetic Elements: Detection of Changes in Maize DNA at the Shrunken Locus Due to the Intervention of Ds Elements, DOE Technical Report, May 1980
Transposable Elements and Genetic Instabilities in Crop Plants, DOE Technical Report, April 1981
How Jumping Genes Were Discovered, Nature Structural Biology, Vol. 8, No. 4, April 2001McClintock research referenced in the above reports include:
• Mutable Loci in Maize (1952)
• Mutation in Maize (1953)
Barbara McClintock, The National Health Museum
Barbara McClintock, Marine Biological LaboratoryTop
Additional Web Pages:
Nobel Lecture by Barbara McClintock, nobelprize.org (video)Top