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Scientist Spotlight: Barbara McClintock

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Lisa Winter

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clockOct 23 2013, 01:01 UTC
45 Scientist Spotlight: Barbara McClintock
Smithsonian Institution

If you know you are on the right track, if you have this inner knowledge, then nobody can turn you off... no matter what they say.” -Barbara McClintock

 

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After observing maize for several generations, Barbara McClintock noticed shifts in the coloring patterns on the kernels. She theorized that certain parts of the genes were able to be rearranged between chromosomes, and the theory of "jumping genes" was born in the 1940s, although the details of how this happened were initially unknown to her. Experiments performed with more sophisticated technology in the coming decades would verify her theory and in 1983 she became the first woman to win an unshared Nobel Prize in Physiology or Medicine.

 

"Jumping genes," correctly known as transposable elements (TEs) or transposons, are found in all organisms ranging in complexity from humans all the way down to bacteria. In humans, there are two major types of transposons: long interspersed nuclear elements (LINEs) that are around 6 kilobase pairs (kb) long, and short interspersed nuclear elements (SINEs) that are only 100-500 base pairs (bp) long.

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The exact function of transposons is currently unknown though they do comprise a considerable part of our genome - almost 50%. Most of this does not code for protein and has been labeled “junk DNA” in the past. However, that is an incredibly poor name given the amount of activity that occurs within these genes. Some theorize that LINEs and SINEs helped shape some genes, giving it evolutionary value, though they have also been shown to mutate genes and cause disease, such as hemophilia as well as breast cancer from mutations on BRCA1 and BRCA2 and can be passed down throughout familial lineages.

 

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In addition to receiving the Nobel prize, Barbara McClintock was given numerous prestigious awards including: Albert Lasker Award, Benjamin Franklin Medal, Thomas Hunt Morgan Medal, 14 honorary doctorates, and the National Medal of Science, the highest scientific honor in the United States.

 

Though McClintock passed away in 1992, the legacy of her discovery lives on and thrives in cytogenetics. Transposons are used as a vector to modify a genetic sequence, allowing researchers to tag, identify, isolate, and clone specific genes, making her work indispensable in modern laboratories.


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