GNN - Genetics and Genomics Timeline

Amidst much interest in cell structure and development, in 1887 Theodor Boveri began investigating chromosomes. He was inspired by the first complete description of them two years earlier, together with hints that they might convey something of the secret of heredity. He wanted to discover, he later wrote, "those processes whereby a new individual with definite characteristic is created from the parental generative material." In studies published from 1887 to 1890, Boveri made several key observations about the way that chromosomes behave during cell division.

Theodor Boveri
Courtesy American Philosophical Society

• Chromosomes remain organized and individual structures through the process of cell division. Boveri worked with eggs of Ascaris megalocephala, a parasitic worm with just four chromosomes, publishing an exhaustive study in 1888. During the "interphase" just before cell division, the chromosomes could not be individually distinguished—indeed, they seemed to disappear. But Boveri, using the light microscope, showed that the same arrangement and shape of chromosomes could be found in the daughter cells both before and after mitosis, or somatic cell division. Under his interpretation, chromosomes were highly organized units. Because inheritance demands continuity from generation to generation, Boveri began to suggest that chromosomes were involved in heredity.

• Sperm and egg contribute the same number of chromosomes. Boveri went on to work with sea urchin eggs. He discovered that, during fertilization, the nuclei of sperm and egg do not fuse, as previously thought. Rather, each contributes sets of chromosomes in equal numbers. With this study, published in 1890, Boveri provoked great interest in the chromosomes; but his idea that they were central to inheritance frequently met with skepticism.

Boveri's early studies set the stage for his hypothesis, to be put forward at the turn of the twentieth century, after the rediscovery of Mendel's laws, that chromosomes transmit hereditary characteristics.

A professor of zoology and comparative anatomy at the University of Würzburg, Boveri combined exceptional observational skills with great theoretical acuity. He possessed a willingness to advance controversial hypotheses and defend them vigorously. Toward the end of his life, in 1914, he made the provocative and far-sighted suggestion that abnormal chromosomes might be responsible for cancerous tumors.

Baltzer, F. Theodor Boveri. Science 144, 809-815 (1964).

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