Summary

In Calcutta, Siddhartha Mukherjee and his father visit the house where his father grew up. They discuss the idea of genes and the history of mental illness in the family as "a flaw in identity, a genetic illness, a blemish that cannot be separated from the self" (91).

In the late 1920s, there was much talk about the links between genes and identity, but no one yet understood the identity of a gene itself, how it works, what it is made of, etc. At Columbia University, a scientist named Thomas Morgan "wanted to uncover the physical basis of heredity" (92). He built on the work of earlier scientists who had already postulated that genes are carried on chromosomes. To delve further into the nature of genes themselves, Morgan carried out extensive experiments on fruit flies. Morgan discovered that genes do not always behave independently...