BiologyOther

Martha Chase: The Underappreciated Geneticist

Martha Chase was an American geneticist. In 1952, during the “Hershey-Chase Experiments,” she accompanied Alfred Hershey, helping to experimentally confirm that DNA, not protein, is the genetic material of life [1]. This discovery was awarded the Nobel Prize in Physiology or Medicine in 1969, yet excluded Chase [2]. There is not much information about the level of “intellectual contribution” Chase played in the experiment, but, given that she was listed as a co-author on the results paper (which was not common practice as she was a research assistant), she is believed to have played a key role. [3,4] Because of this, one could speculate that her Nobel Prize exclusion had patriarchal undertones. There is also a lot of potential for discussion regarding the inclusion of research assistants in general for Nobel Prizes [5].

Hershey-Chase Experiments [1]

The Avery–MacLeod–McCarty experiment, published in 1944, first suggested that DNA, not proteins, was responsible for hereditary information, but there was some unwillingness within the scientific community to accept this, leaving it to the Hershey–Chase experiment to confirm DNA as the genetic material [6,7].

Hershey and Chase used a simple model organism for their experiment called a bacteriophage (a virus which infects bacteria). Viruses infect organisms via inserting hereditary material in the host organism to produce more copies of itself. The bacteriophage virus has a protein coat and a DNA cover. To find out which is inserted into the bacteria, they ran 2 experiments and labelled one with a radioactive tag. Radioactive sulfur for the protein and radioactive phosphate for the DNA. Phosphate was found in DNA and sulfur was found in proteins and not in each other. They intended to check if the radioactive signal was found inside or outside of the cell.

Firstly, they needed to separate the bacteria from the viruses attached to the outside using a Waring blender (similar to the one that’s used to make milkshakes). Once they have been detached, they are centrifuged (centrifuge is a force, arising from the body’s inertia, the tendency of an object to stay in its current state of motion, which appears to act on a body moving in a circular path and is directed away from the centre around which the body is moving) [8]. The larger bacteria then separates to the bottom. When they prepared phosphate labelled DNA virus and mixed it with bacteria, most of the DNA was injected into the bacteria and present in the next virus generation. This added to the evidence, indicating that DNA was the genetic material of life, or at least that DNA had “some role” in bacterial reproduction.

Conclusion

Martha Chase was a woman who played an integral part in the classic biology experiment that addressed an important question. Using an effective and elegant model organism and experiment design, Chase and Hershey’s findings had numerous implications across many fields such as forensic science. While she may have been overlooked by the scientific community during her time, as visibility and diversity increase in STEM fields, she will be remembered and honored for her intelligence, dedication, and passion.

References

  1. Hershey, A. D., and Martha Chase. 1952. “INDEPENDENT FUNCTIONS OF VIRAL PROTEIN AND NUCLEIC ACID IN GROWTH OF BACTERIOPHAGE”. The Journal Of General Physiology 36 (1): 39-56. doi:10.1085/jgp.36.1.39.
  2. “The Nobel Prize In Physiology Or Medicine 1969”. 2020. Nobelprize.Org. https://www.nobelprize.org/prizes/medicine/1969/summary/.
  3. Clark, Clare. 2020. “Libguides: Women’s History Month: CSHL Women In Science”. Cshl.Libguides.Com. https://cshl.libguides.com/c.php?g=647154&p=4558333.
  4. Bibel, Brianna. 2020. “Martha Chase”. The Bumbling Biochemist. https://thebumblingbiochemist.com/wisewednesday/martha-chase/.
  5. “Statutes Of The Nobel Foundation”. 2020. Nobelprize.Org. https://www.nobelprize.org/about/statutes-of-the-nobel-foundation/.
  6. Avery, Oswald T., Colin M. MacLeod, and Maclyn McCarty. 1944. “STUDIES ON THE CHEMICAL NATURE OF THE SUBSTANCE INDUCING TRANSFORMATION OF PNEUMOCOCCAL TYPES”. The Journal Of Experimental Medicine 79 (2): 137-158. doi:10.1084/jem.79.2.137.
  7. DEICHMANN, UTE. 2004. “Early Responses To Avery Et Al.’S Paper On DNA As Hereditary Material”. Historical Studies In The Physical And Biological Sciences 34 (2): 207-232. doi:10.1525/hsps.2004.34.2.207.
  8. “Centrifugal Force”. 2020. Lexico. Lexico.com. https://www.lexico.com/definition/centrifugal_force.

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