Since 1987, the U.S. has observed Women’s History Month every March to celebrate women’s contributions to history, culture, and society. There is also a great deal of historical women who have contributed to the world of science. At the HudsonAlpha Institute for Biotechnology, scientists are exploring and growing the knowledge and possibilities of genomics. Geneticist Rosalind Franklin and scientist Barbara McClintock shared that same vision.
The Double Helix
Although born in London, England, Rosalind Franklin had an international impact in the science field. From the young age of 15, Franklin knew that she wanted to be a scientist. Despite her father’s objection against higher education for women, Franklin studied physics at Newnham College, Cambridge in 1938. After graduation, she went on to work at the British Coal Utilisation Research Association, where she studied carbon and graphite microstructures. After earning her Ph.D. in physical chemistry from Cambridge University, Franklin began working in Paris at the Laboratoire Central des Services Chimiques de l’Etat with crystallographer Jacques Mering. There, Mering taught Franklin X-ray diffraction analysis, which would prove beneficial in a significant discovery.
In 1951, Franklin moved back to London and was awarded a fellowship at King’s College under John T. Randall. Originally, she was asked to work on X-ray diffraction of proteins and lipids in solutions, but assistant lab chief, Maurice Wilkins suggested Franklin investigate DNA instead. Wilkins had begun X-ray diffraction work on DNA samples so he was under the impression that Franklin would be assisting him. Randall however was not under the same impression and said only Franklin and graduate student Raymond Gosling would be conducting any DNA research.
This misunderstanding damaged Franklin’s professional relationship with Wilkins, but it also lead to a groundbreaking discovery. The team continued working with X-ray diffraction, taking photos of DNA and discovered there were two forms, wet and dry or “B” and “A,” which produced very different pictures. She observed that the “B” form had a helical structure and named the image Photograph 51. Her mathematical analyses of the “A” form did not indicate a helical structure and Franklin spent more than a year trying to resolve the differences. In 1953, it was concluded that both forms had a helical structure. Unfortunately, this conclusion was not credited to Franklin.
Around the time of Franklin’s discovery of Photo 51, Wilkins had been working at the Cavendish Laboratory in Cambridge with his friend Francis Crick and colleague James Watson. The three were also trying to discover the structure of DNA and in doing so, Wilkins found Franklin’s Photo 51 and her unpublished research. Later, Crick and Watson published their findings in Nature and were credited with the discovery of the double helix structure.
Franklin was only allowed to leave her fellowship at King’s College under the condition that she would not continue her work with DNA. She relocated to J.D. crystallography laboratory at Birkbeck College where she turned her attention to coal, plant viruses, particularly the tobacco mosaic virus, and the structure of RNA. Although Franklin did not receive recognition for her work with DNA until years later, she went on to publish 17 papers on viruses and laid the foundation for modern virology.
“The results suggest a helical structure [of DNA], which must be very closely packed,
containing probably 2, 3, or 4 coaxial nucleic acid chains per helical unit
and having the phosphate groups near the outside.” — Rosalind Franklin
As the daughter of a physician, Barbara McClintock had an early interest in science. That interest lead to one of the most profound discoveries in the world of genetics. Born on June 16, 1902 in Hartford, Connecticut, McClintock began her scientific career at Cornell University in 1919, receiving her bachelor’s degree in biology and a Ph.D. in botany. McClintock remained at Cornell to continue her research in cytogenetics, a branch of genetics that is concerned with the study of the structure and function of the cell, especially the chromosomes.
Using traditional staining techniques, McClintock was able to examine, identify and describe individual corn chromosomes. By 1929, she had redefined these techniques to discriminate between each of the ten maize chromosomes, allowing researchers to link genetic data to the behavior of chromosomes. Over the next few years, McClintock had published nine papers on maize chromosomes, including one in collaboration with colleague Harriet Creighton entitled, “A Correlation of Cytological and Genetic Crossing-over in Zea mays.” The paper explained that chromosomes formed the basis of genetics.
McClintock’s discovery earned her a presidential election in 1944 into the Genetics Society, making her the society’s first female president. In 1941, she was offered a research position at the Carnegie Institution of Washington’s Department of Genetics at Cold Spring Harbor. It was here that she began experimenting with variations in the coloration of corn kernels, and discovered that genetic information is not always stationary.
During her observation, McClintock identified two dominant loci, which she named Dissociator (Ds) and Activator (Ac). She found that the loci could change position or transpose within the chromosome. At the time, genes were considered to be stable entities. McClintock not only discovered these mobile elements, now called transposons, but that depending on where they are inserted into a chromosome, they could alter the expression of other genes.
The world was not so welcoming when McClintock revealed her discovery. “They thought I was crazy, absolutely mad,” McClintock said. Her research was ahead of its time, so it was difficult for the science community to accept the concept of transposition. The negative reaction from fellow scientists was very discouraging to McClintock and she eventually stopped publishing any work on the subject.
In the 1960s and 1970s, scientists began to verify McClintock’s earlier findings when they observed the “jumping genes” in bacteria, yeast and bacteriophages. By this time, new technology emerged that allowed scientists to show the molecular basis of transposition. By 1983, McClintock finally received the recognition that she deserved by winning the Nobel Prize for Physiology and Medicine, making her the first woman to be the sole winner of the award.
“When you know you’re right, you don’t care what others think.
You know sooner or later it will come out in the wash.” — Barbara McClintock