Sager, Ruth

born Feb. 7, 1918, Chicago, Ill., U.S.

died March 29, 1997, Brookline, Mass.

U.S. geneticist.

She received her Ph.D. from Columbia and later taught at Hunter College and Harvard University. Questioning the traditional belief that chromosomal genes are the only apparatus for transmitting genetic information to a cell, she discovered (1953) in the alga Chlamydomonas the existence of a second genetic transmitting system, a gene not located on the alga's chromosomes that controls the cell's sensitivity to the antibiotic streptomycin, and she observed that both male and female Chlamydomonas can transmit the nonchromosomal gene.

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▪ 1998

      American geneticist (b. Feb. 7, 1918, Chicago, Ill.—d. March 29, 1997, Brookline, Mass.), conducted groundbreaking research on where genetic material is found in cells; her findings changed the way that biologists view cell heredity. Later in her career she studied the genetic mechanisms related to cancer. Sager entered the University of Chicago at age 16, sampling the liberal arts before a chance encounter with a survey course on biology ignited her interest in the field. She graduated with a B.S. in 1938. Graduate work in plant physiology followed at Rutgers University, New Brunswick, N.J., where she received an M.S. in 1944. She continued graduate studies in genetics at Columbia University, New York City, earning a doctorate in 1948. Sager joined the research staff at the Rockefeller Institute (now Rockefeller University), New York City, as an assistant in 1951. There she challenged the prevailing theory that inherited characteristics are transmitted exclusively by the genes in the chromosomes, which are found in a cell's nucleus. In studying heredity in Chlamydomonas alga, she discovered that a gene located outside the chromosomes also transmits inherited characteristics. Nonchromosomal genes were later shown to be ubiquitous in living organisms. In 1955 Sager joined Columbia University's zoology department, where she expanded her understanding of how nonchromosomal genes work. She served as a professor of biology at Hunter College, New York City, from 1966 through 1975, when she was appointed professor of cellular genetics at Harvard University and head of Harvard's Dana-Farber Cancer Institute. Sager's extensive research into the mechanisms associated with cancer involved tumour suppressor genes, breast cancer, and the genetic means by which cancer multiplies. Her numerous prizes included the Gilbert Morgan Smith Medal, the National Cancer Institute's Outstanding Investigator Award, and a Guggenheim fellowship.

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▪ American geneticist

born Feb. 7, 1918, Chicago, Ill., U.S.

died March 29, 1997, Brookline, Mass.

      American geneticist chiefly noted for recognizing the importance of nonchromosomal genes.

      Sager attended the University of Chicago (B.S., 1938), Rutgers University (M.S., 1944), and Columbia University (Ph.D., 1948) and then undertook genetic research at the Rockefeller Institute (now Rockefeller University), New York City. In 1955 she returned to Columbia, where she worked as a research associate until 1966, when she was appointed professor of biology at Hunter College. In 1975 she began working at the Dana-Farber Cancer Institute, Boston, later becoming chief of cancer genetics. She was also professor of cellular genetics at the Harvard Medical School from 1975 to 1988.

      While at the Rockefeller Institute, Sager began to question the traditional belief that all the genes governing heredity were to be found arranged linearly on the chromosomes of cell nuclei. In 1953 she discovered in the alga Chlamydomonas a second genetic-transmitting system: not located on the chromosomes of the alga. This gene governs the cell's sensitivity to the antibiotic streptomycin. Her experiments showed that the many nonchromosomal genes in Chlamydomonas could be passed on by either partner in sexual reproduction, that they controlled a variety of hereditary characteristics, and that they replicated and remained active through successive generations. In the 1960s research inspired by her pioneering studies showed that chloroplasts and mitochondria in cells of organisms throughout the evolutionary chain contain genetic materials that apparently synthesize proteins and other substances and largely regulate their own development. Her work became very influential in the early years of molecular genetics through Cell Heredity (1961), a textbook written with Francis J. Ryan. Sager was elected to the National Academy of Sciences in 1977.

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