Walter Stanborough Sutton (April 5, 1877 – November 10, 1916) was an American geneticist and biologist whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms. This is now known as the Boveri–Sutton chromosome theory. Early life Sutton was born in Utica, New York, and was raised on a farm as the fifth of seven sons to Judge William B. Sutton and his wife, Agnes Black Sutton, in Russell, Kansas. On the farm, he developed a mechanical aptitude by maintaining and repairing farm equipment, an aptitude that proved helpful later as he worked on oil drilling rigs and with medical instrumentation. University of Kansas After graduating high school in Russell, he enrolled at the University of Kansas in engineering in 1896. Following the death of his younger brother (John) from typhus in 1897, Sutton switched his major to biology with an interest in medicine. While at the University of Kansas, both he and his older brother, William Sutton, played basketball for Dr. James Naismith. Sutton distinguished himself as a student by being elected to both Phi Beta Kappa and Sigma Xi and receiving both bachelor's and master's degrees by 1901. For his Masters thesis, he studied the spermatogenesis of Brachystola magna, a large grasshopper indigenous to the farmlands upon which Sutton was raised. Columbia University Considering the advice of his mentor at KU, Dr. C. E. McClung, Sutton moved to Columbia University for further study of zoology under Dr. Edmund B. Wilson. It was here that Sutton wrote his two significant works in genetics – “On the morphology of the chromosome group in Brachystola magna” and “The chromosomes in heredity”. Effectively, Sutton could now explain “why the yellow dog is yellow”. The German biologist Theodor Boveri independently reached the same conclusions as Sutton, and their concepts are often referred to as the Boveri–Sutton chromosome theory. Sutton's hypothesis was widely accepted by most scientists, particularly cytologists, at the time. The continued work of Thomas Hunt Morgan at Columbia brought the theory to universal acceptance by 1915 through his studies of Drosophila melanogaster, the fruit fly, even as William Bateson continued to question the theory until 1921. Sutton did not complete his PhD in Zoology as he originally planned. At the age of 26, he returned to the Kansas oil fields for 2 years.