How did Thomas Hunt Morgan use fruit flies?
I chose Drosophila because it breeds rapidly, produces many offspring, and has only four chromosomes, making it ideal for experimental genetics. In my lab at Columbia University, we raised thousands of flies in milk bottles, feeding them mashed bananas. We exposed them to X-rays to induce mutations, then tracked visible traits like eye color, wing shape, and body color across generations. By counting the ratios of traits in offspring, we could map the relative positions of genes on chromosomes. For instance, the white-eye mutation appeared only in males, revealing it was sex-linked. This method was inductive: we let the numbers guide us. The fly tells us what is true—we just had to do the experiment.
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