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Faces of Science: Maclyn McCarty

The Secret Life of Scientists and EngineersThe Secret Life of Scientists and Engineers

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Mariana Cook’s book , “Faces of Science,” portrays 77 scientists who have made many of the most important discoveries of our time. Each photograph is accompanied by a personal essay written by the scientists. The portraits in this online series are accompanied by excerpts from those essays. For more information, please visit Mariana Cook’s website: .

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Maclyn McCarty - Photos and Text ©Mariana Cook “Faces of Science”

My mother said she could remember that at age 10 I read some scientific material that had been sent to my father, three or four books on things going on in biology. She also remembered that at age 10 I said I was going to be a doctor and do research. I never changed my mind. My high school in Kenosha, Wisconsin, had no German-language classes, so I went across town after school to get tutoring in German from a Lutheran minister. I had read that Johns Hopkins Medical School required a reading knowledge of French and German. It’s not easy to say why I chose Stanford University, but that had to do with something I had read, in this case about the work there in medical research.

Upon graduation from medical school, I stayed on at Hopkins as a pediatric intern and resident with Dr. Edwards A. Park, who encouraged me to pursue a research career and helped me get a postdoctoral position with William S. Tillett at NYU. It was Tillett who suggested I apply for a National Research Council Fellowship for financial support and then contacted Dr. Oswald Avery when the NRC awarded me the fellowship, with the suggestion that I go to Rockefeller for further training. Avery’s laboratory at the Rockefeller had been working for a long time with an organism called pneumococcus, the cause of pneumonia. Fred Griffin in England reported on a phenomenon he discovered, that by putting the bacteria into mice, the organism was transforming from one type to another. Avery picked up on this problem to try to find out why.

As time went on, it became clear that the transformation involved a change in one type of pneumococcus that was induced by a substance extracted from another kind. This change was predictable and permanent, being transmitted from generation to generation. It had all the earmarks of what we would call today the transfer of genetic information.

The varied types of pneumococcus were all very similar, but it turned out that they were different in their surface, called a capsule. Without capsules, the bacteria are not infectious. What we did was extract cell-free material from one type of bacteria and mix it with living bacteria of another type lacking capsules. The second type would then produce capsules of the first type. Gradually a number of pieces of evidence emerged to show that the transforming agent was DNA. It was the first experimental evidence that the genetic material in cells is DNA. In 1944, Oswald Avery, Colin MacLeod and I published this finding in a seminal paper in the Journal of Experimental Medicine, although the paper was not widely acknowledged at the time. Nonetheless, our discovery played a pivotal role, not only in the identification of DNA’s structure by Watson and Crick nine years later, but it was also critical in the initial foundation of the fields of molecular biology and genetic engineering.

I have often said and written that the continued excitement in the research of those early days could hardly be duplicated again. Science today has changed in a way that’s not good. There is too much involvement of fiscal gain in research. Researchers are dependent on financial gain and therefore work more for that than for what the research might do, what the value of it is for the cure of disease or for a variety of medical problems. As soon as you stared getting things patented, you got involved heavily with the financial side. You can tell what was different in the early days because—for example, at Rockefeller—a whole slew of things were first turned up and not patented at all. The researchers weren’t even thinking about getting the discoveries protected. People in medical science today, by and large, are much more oriented toward the dollar side of their work than when I started out.