Barbara Mcclintock

Decent Essays

Ever since graduate school, Barbara McClintock liked to study corn. And this started at Cornell! Her interest in genetics started with her first undergraduate genetics course. Her interest earned her a phone call from her genetics professor, Dr. Hutchison, which invited her to a graduate level genetics course; this call “cast the die” for her future—she intended to pursue genetics. At that time period, women were not allowed to major in genetics in graduate school. This did not stop McClintock. Inspired by a previous cytology course that delved into the structures and behaviors of chromosomes during mitosis and meiosis, she began working on corn chromosomes. She eventually developed a technique that allowed her to visually identify each corn …show more content…

There, she could freely pursue her research without having to teach or ask for grant money. The institution also allowed her to avoid the negativity often targeted at women scientists. At Cold Spring Harbor, she made her seminal discovery: transposons, or “jumping genes”. This all went back to chromosome 9 breakage. On chromosome 9, through recombination frequencies, she identified two new gene loci; one was called “dissociator” (Ds) and the other, named “activator” (Ac) and also mapped four traits. She noticed that when activator locus was absent, there was chromosomal breakage, and the corn was yellow/white. She figured that this breakage must have occurred at a gene that caused corn to have purple color. However, when Ac was present, Ds somehow mapped somewhere else on the chromosome, and the corn had its purple color. She reasoned that the presence of Ac must have caused Ds to “jump” out of the gene enabling purple color into another random …show more content…

She emphasized that transposition wasn’t just about turning corn color genes on and off, but also possibly a way for the genome to reorganize itself quickly as a response to environmental conditions. However, most scientists were puzzled and hostile towards her ideas. Though she eventually gave up trying to convince them and stopped publishing her data, she didn’t let that get her down, because she “knew she was right”. But there were geneticists who did appreciate her work. In the 1970s, a molecular basis of transposition was discovered, and the connection between transposition and antibacterial resistance and cancer was made. Starting in 1971, McClintock began to receive a long list of awards, including the National Medal of Science awarded to her by President Nixon, and in 1983, she won the Nobel Prize in Physiology or Medicine for her work on transposition. Afterwards, she remained at Cold Spring Harbor and gave talks on her work until her death. McClintock’s work is relevant even nowadays. It was found that a large percentage of many genomes including that of humans is composed of transposons. Because transposons can jump around and insert themselves into protein-coding sequences, they could cause cancer. In order for the cells to protect their genomes, recently, small RNAs called piRNAs were discovered to target histone methylation to transposon sequences to stop the transposons from moving around. Additionally,

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