German Joseph Muller American geneticist, student of Thomas Hunt Morgan, Nobel Prize winner in physiology or medicine (1946). Date of Birth: 21.12.1890 Country: USA

Biography of Hermann Joseph Muller

Hermann Joseph Muller was an American biologist and geneticist, known for his groundbreaking work in the field of genetics. He was born in New York City and was the youngest of two children in his family. His father, also named Hermann, had planned to become a lawyer but ended up taking over the family foundry. His mother, Frances Louisa Lyon, was of English Sephardic descent.

Muller's father passed away when he was just nine years old, but he had already instilled in him a passion for science. Muller and his older sister attended a public school in Harlem, and in 1907, he graduated from Morris High School in the Bronx. As an exceptional student, Muller received a scholarship to Columbia University, a leading center for genetic research. There, he organized a student biological club, much like he had done in high school.

In 1910, Muller graduated from Columbia University with honors, and the following year, he earned a Master of Science degree in physiology with a thesis on nerve impulse transmission. After completing his university studies, Muller received a scholarship and conducted experimental physiology research at the Cornell University Medical College in New York. During this time, he maintained contact with two young friends from the Columbia Biological Club, Alfred Sturtevant and Calvin Bridges, who were studying chromosomal inheritance in the fruit fly Drosophila in Thomas Hunt Morgan's laboratory. Muller joined this group in 1912 when he became a teaching fellow in the Department of Zoology.

Through their genetic research on Drosophila, Muller and his colleagues demonstrated that genes are grouped together, can be separated, and can undergo recombination according to Gregor Mendel's principles of genetics. In his doctoral dissertation in 1916, Muller conclusively proved that the four groups of linked genes they had discovered corresponded to the four chromosomes in the nuclei of Drosophila cells. This discovery convinced Morgan, who had previously been skeptical, that Mendelian genes were not just theoretical symbols but real units located in chromosomes. The research findings of Muller's scientific group were published in a book titled "The Mechanism of Mendelian Heredity" in 1915, which discussed the principles of "classical" genetics before the advent of biochemical research.

Feeling that many of his ideas, especially the theoretical ones, were not recognized at Columbia University, Muller accepted a collaboration offer from Julian Huxley at the Rice Institute in Houston, Texas, and relocated there in 1915. He later returned to Columbia University for two years (1918-1920) before becoming a professor of zoology at the University of Texas at Austin.

In 1923, Muller married Jessie Marie Jacobs, a mathematics instructor and co-author of some of his publications. They had one son together. Muller's interest in genetics was supported by Charles Darwin's theory of natural selection, which proposed that new genetic variations, or mutations, occur constantly and randomly in populations of living organisms. According to this view, since the changes are small, evolution occurs in gradual steps rather than large leaps.

Expecting that the majority of natural mutations would be unfavorable for species survival, Muller bred varieties of fruit flies in which the chromosomes were marked with harmless genetic variants for identification purposes. The marked chromosome carrying a harmful mutation should, in theory, disappear from the genetic line; the frequency of such disappearances could then serve as a measure of mutation rates. In 1920, Muller and his colleague Edgar Altenburg from Columbia University conducted the first measurements of mutation rates. While working at the Rice Institute, Muller discovered that most mutations were harmful or lethal. He also showed that the mutation rate was independent of environmental factors and occurred at a constant rate, regardless of whether it was needed or not. Muller hypothesized that environmental factors like X-rays, discovered by Wilhelm Rontgen in 1895, could have a genetic effect. Normally, genes are very stable, and it takes an extremely high level of energy, such as in X-ray exposure, to damage them. Since X-rays affect individual molecules, they can damage individual genes without affecting others. In 1926, Muller found that X-rays actually increased the mutation rate in his marked fruit fly strain by hundreds and thousands of times compared to the norm.

His discovery, which demonstrated that heredity and evolution could be intentionally altered under laboratory conditions, caused a sensation. After publishing his research in the journal "Science" in 1927, Muller suddenly became well-known and respected. However, due to exhaustion and growing financial difficulties caused by the 1929-1930 economic crisis, he attempted suicide in early 1932. After recovering from his depression, he returned to Germany with a Guggenheim Fellowship and spent a year at the Kaiser Wilhelm Institute for Brain Research in Berlin, working in the genetics department led by Nikolay Timofeev-Ressovsky. He then accepted an invitation from Nikolai Vavilov, the director of the Institute of Plant Industry of the USSR Academy of Sciences, to come to Leningrad as a leading geneticist for studying gene mutations. In 1935, he divorced Jessie Jacobs. Muller left the USSR in 1939 to participate in the Spanish Civil War. Over the next three years, he worked at the Animal Genetics Institute at the University of Edinburgh in Scotland, where he met Dorothea Kantorowicz, a German immigrant. They got married in 1939, and they had a daughter.

Upon returning to the United States in 1940, Muller temporarily held a position as a biology professor at Amherst College in Massachusetts. In 1943, he participated as a consultant in the development of the Manhattan Project, and after the war, he worked for the United States Atomic Energy Commission. In 1945, he became a professor of zoology at Indiana University in Bloomington. Muller was awarded the Nobel Prize in Physiology or Medicine in 1946 "for the discovery of the production of mutations by means of X-ray irradiation." In his Nobel lecture, titled "The Production of Mutations," Muller summarized his experimental work, which gained new and terrifying significance with the advent of atomic weapons. "With the increasing employment of atomic energy, even in peaceful pursuits," he said, "the problem of providing adequate safeguards against this additional and potent source of constant contamination to human germ plasm will become very important." Among those who, based on Muller's research, advocated for the ban of nuclear testing was Linus Pauling.

In his later years, Muller made significant efforts to change biology education in secondary schools and developed a eugenics program called "Selective Conception," in which the sperm of outstanding men would be frozen for use in conceiving a healthy and intelligent future generation. He expressed his views on these matters in the book "Out of the Night: A Biologist's View of the Future" in 1935. Alongside his genetic research, Muller also conducted the first psychological analysis of the behavior of identical twins raised in different families.

Muller had a passion for various sports, a keen interest in world politics and travel, and a love for literature. In the mid-1960s, he developed heart disease with signs of heart failure, and in 1967, he passed away in Bloomington at the age of 77.

Muller received numerous awards, including the Kimber Genetics Award from the National Academy of Sciences (1955) and the Alexander Hamilton Medal from Columbia University (1960). He was a member of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, the Society for Experimental Biology and Medicine, the American Society of Zoologists, the American Society of Genetics, the Genetics Society of Great Britain, and the American Philosophical Society.