(SciShow Intro plays)

Hank Green: Some of the most important principles in modern genetics were either discovered, proven, or first conceived of by a woman who you have never heard of who spent forty years of her life studying corn.  More than 20 years before Watson & Crick identified the structure of DNA, Barbara McClintock was inventing the field of cytogenetics, the study of the structure and function of chromosomes.  

In 1931, through her pioneering microscopic techniques, she was the first to prove that genes were physically located on chromosomes.  She did that by being the first to also show that chromosomes swapped bits of genetic information by crossing over when sex cells are formed.  This crossover is one of the most important aspects of reproduction because it explains why sex cells from the same individuals can produce offspring that are different from each other.

 In the 1940s, McClintock focused on the puzzling color patterns of Indian corn.  She wondered why some kernels were white and some were brown and some were purple and some were white with speckles.  It was thought at the time that the speckled kernels were mutated white ones, but no one could figure out what caused the mutation.  Well, after breeding inhuman numbers of maize plants over many generations, she realized that the only way that this could happen is if sections of the plants genome moved from one location to another, sometimes landing smack dab in the middle of a gene for color, making the kernel look like it lost a paintball tournament.  In this way, McClintock discovered what we now call transposable elements, or jumping genes.  Turns out that there are stretches of DNA in pretty much every type of organism that can move one location to another and its one of the most important sources of genetic mutations, including in humans.

Being a lady scientist in the 1940s though, meant that you couldn't do face-blisteringly awesome science and receive proper recognition.  Maybe she should have been baking cakes.  Her discovery, when it wasn't ignored, was ridiculed, but she kept researching and she did a little more genetic pioneering, like in 1951 when she discovered that genes were silenced when stuff in a cell's nucleus, later discovered to be enzymes, covered them up.  McClintock eventually got so tired of the ridicule that her ideas received that she stopped publishing her research.  It wasn't until the 1970s when scientists could actually observe the processes McClintock described that they felt bad for being such patronizing assfaces.  So in 1983, 35 years after she published her first paper on transposition, Barbara McClintock was awarded the Nobel Prize for Physiology or Medicine "for her discovery of mobile genetic elements" and she remains the only woman to receive an unshared Nobel Prize in that category. 

Thank you for watching this episode of SciShow.  If you enjoyed, please go to YouTube.com/SciShow and subscribe.  If you have any ideas or questions or comments, please leave them on Facebook or Twitter or down in the YouTube comments below.  Goodbye.  

(SciShow Endscreen plays)