Walter Sutton spent most of his childhood on the family farm in Kansas with his parents and six brothers. He entered the University of Kansas at Lawrence in 1896 to study engineering. The following year, after his youngest brother died of typhoid fever, Sutton turned to a career in medicine. He began studying biology at the university and was strongly influenced by a zoology instructor, Clarence E. McClung (1870-1946). In the late 1890s, Sutton was attempting to understand the function and structure of chromosomes by experimenting with grasshoppers. After earning his master's degree under McClung in 1901, he went on to Columbia University for his doctorate. Although he did not complete his thesis, he made a very important contribution to science: the Chromosomal Theory of Inheritance. (Theodor Boveri, who developed a similar theory around the same time, shares the credit for the discovery.)

Cytologists already suspected that chromosomes played a role in heredity, but it was Sutton who demonstrated the connection between the behavior of chromosomes and the laws of Gregor Mendel. Sutton made detailed diagrams of grasshopper chromosomes that showed various phases of development--including how chromosomes behave during mitosis (formation of daughter cells during cell division) and meiosis (formation of sex cells). He determined that all chromosomes exist in pairs, one from each parent. Sutton also asserted that these chromosomes contain the physical mechanism that explained the principles in Mendel's newly discovered works.

After leaving Columbia to work in the oil industry for two years, Sutton returned to the university, where he received his M.D. in 1907. He worked as a surgeon at Roosevelt Hospital in New York, New York, for two years before settling in Kansas City, Kansas. He died of a ruptured appendix in 1916.