Hermann J. Muller: IU Nobelist

The "Fly Room" at Columbia

Muller 1914 A factor for the fourth Chromosome

This draft of a paper on the fourth chromosome of Drosophila became Muller's first scientific publication. The patchwork penmanship stays with him for his whole career. It can even be found in his childhood writings.

Muller’s relationship with the fly room was complicated. First, he was simply busier than some of the other members of the lab--juggling several other jobs ensured he was unable to fully participate in laboratory culture. Unlike his colleagues Calvin Bridges and Alfried Sturtevant, Muller was not at first financially supported by Morgan’s lab. More problematic were his intellectual issues with Morgan. In Muller’s view, Morgan’s saving grace was that he had the good sense to listen to his students. However, Morgan’s skepticism about chromosome theory and stubborn demands for straightforward experimental demonstration were endlessly irritating to the young Muller who had an uncanny gift for envisioning complex breeding experiments and what they said about chromosome structure. And it was no doubt difficult for Muller to give much credit to Morgan for adopting chromosome theory when E. B. Wilson, whom Muller greatly admired, had done so years earlier.

The one discovery Muller gave Morgan indisputable credit for--and arguably the most important discovery to come out of the lab--is the phenomenon of crossing-over. The great insight of Mendelism was that inheritance was particulate, meaning that crosses would result in fixed ratios in offspring with distinct traits rather than just intermediate traits. One of the associated assumptions was that traits were inherited independently. For instance, if a pea plant had a ¼ chance of being yellow, and a ¼ chance of being wrinkled, then it had a 1/16 chance of being yellow and wrinkled. However, experimentalists like Thomas Hunt Morgan were finding that certain traits were inherited together far more often than would be expected by chance. It was this evidence, together with the urging of his students, that finally convinced Morgan to fully adopt chromosome theory. The fly room members reasoned that if genes for two separate traits were on the same chromosome, that would explain why they were usually inherited together.

← Page 2
Page 4 →
Page 3