Welsh, Michael J., and Alan E. Smith. "Cystic Fibrosis." Scientific American 273 (1995): 53-59.

Delbrück, Max

Physicist, Molecular Biologist 1906-1981

Max Delbrück made major contributions to the understanding of replication and viral function. Raised in Berlin in a distinguished family of German intellectuals, Delbrück trained as a physicist with Niels Bohr and other leaders in the field of quantum mechanics. In the early 1930s his interests turned toward biology and the nature of the gene. This was only thirty years after the rediscovery of Mendel's work and twenty years before Watson and Francis Crick discovered the structure of DNA. With two colleagues, he published a theoretical paper on quantum mechanical restrictions on gene structure. These ideas were popularized by the physicist Erwin Schrödinger in the book What is Life?, which inspired many young midcentury scientists to join the quest to understand the gene.

Max Delbrück.

bacteriophages viruses that infect bacteria

Delbrück moved to the United States in 1937 to pursue genetics and escape the increasingly repressive atmosphere of Nazi Germany. He first went to Columbia University in New York, where he joined Thomas Hunt Morgan's group to study Drosophila. Soon, however, he became interested in bacteriophages. It was in the understanding of this model system that Delbrück made his greatest contribution.

Bacteriophages are among the simplest genetic systems, and thus provided Delbrück with an elegant tool for exploring fundamental processes of reproduction and mutation. Delbrück collaborated with Salvador Luria and Alfred Chase to work out the fundamental mechanisms of viral replication and to explore the genetics of mutation in this system. This loosely allied trio, and the ever-widening circle of scientists with whom they collaborated, became known as "the phage group." This group conducted training courses at Cold Spring Harbor Laboratory in New York, where they introduced many other biologists to this model system, while inculcating in them their own rigorous and quantitative approach. Watson was one of Delbrück's students in the phage course. The phage group began and shaped the field of molecular genetics, and Delbrück is usually considered the father of this discipline. Delbrück, Luria, and Hershey were awarded the Nobel Prize for physiology or medicine in 1969 for their discoveries in phage genetics.

Later in his life, Delbrück turned his attention to the cellular physiology underlying perception, but the model system he chose for this research, a light-sensitive fungus, had too little in common with animals to make the research strongly relevant to animal perception. He died in 1981. see also Crick, Francis; Morgan, Thomas Hunt; Watson, James; Virus.

Richard Robinson


Fischer, Ernst Peter, and Carol Lipson. Thinking About Science: Max Delbrück and the Origins of Molecular Biology. New York: W. W. Norton, 1988.

Judson, Horace Freeland. Eighth Day of Creation: Makers of the Revolution in Biology. New York: Simon & Schuster, 1979.

Schrödinger, Erwin. What is Life? New York: Cambridge University Press, 1992.

Development, Genetic Control of

Development is the process through which a multicellular organism arises from a single cell. During development, cells become specialized, or differentiated, taking on different functions and forms. The organism develops a characteristic three-dimensional shape, the parts of which (such as limbs and organs) continue to maintain the same relationship to each other even as the organism grows. How the genes in a single fertilized egg dictate the creation of a complex multicellular creature is the central question in the genetic control of development.

While we are often most curious about human developmental processes, very little is known about the genetics of human development specifically, because experimentation on human embryos is forbidden by law and ethics. Instead, the details of genetic control are best understood in several model organisms, including the roundworm (Caenorhabditis elegans), the fruit fly

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