barbara and jumping genes

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" I start with the seedling, and I don't want to leave it. I don't feel I really know the story if I don't watch the plant all the way along. So I know every plant in the field. I know them intimately, and I find it a real pleasure to know them".

– Barbara McClintock -
Quoted in Charles Birch, Biology and the Riddle of Life (1999)

 I of IV:  transposable elements (transposons) what are they?

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II of IV: barbara Mcclintock

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The formal definition of transposons is that they are DNA sequences that move from one location on the genome to another. The verb transpose can be derived from this name which means to change the relative place or normal order of something, with transposons also being called transposable elements, TE or jumping genes. Here is the original paper Barbara McClintock published to the Proceedings of the National Academy of Sciences of the United States of America (PNAS) on "The origin and behavior of mutable loci in maize".

In the late 1940s, she noticed something entirely unexpected, and her story shifted from a notable, albeit traditional, tale of scientific achievement to one tangled with misunderstanding and confusion. Her maize genes started jumping.Genes were meant to be static, beads on the chromosomal string. Indeed, her work in the 1930s seemed to verify this model — genes didn’t move between chromosomes, they had a fixed address, each a little city on a map. And yet, she saw, they moved. Some genes on maize chromosomes could shift position, and in the process, switch other genes on and off. In her eyes, this was a major discovery and seemed to suggest that the movement of genes could control the development of organisms.

III of IV: Dame Ottoline Leyser on Barbara McClintock

Dame Ottoline Leyser (Professor of Botany at the University of Cambridge) talks to Brian Cox about her admiration for Nobel Prize winning geneticist, Barbara McClintock and explains the two great principles she uncovered.

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IV of IV:  transposable elements

Prof. Susan Wessler introduces transposable elements (TEs); small movable pieces of DNA that can insert throughout the genome. She describes their discovery in maize by Barbara McClintock in the 1940's and their impact on the current study of genetics. Wessler goes on to provide more details about TEs and transposase, the enzyme that facilitates insertion of TEs into the target DNA.

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