In people with chronic myelogenous leukemia, the chromosomes in the blood cells swap sections with each other. A section of chromosome 9 switches places with a section of chromosome 22, creating an extra-short chromosome 22 and an extra-long chromosome 9.
Discovered on September 23, 1846, by John Couch Adams. Neptune was the first planet found by mathematical prediction rather than by observation. Unexpected changes in the orbit of Uranus led astronomers to deduce that its orbit was subject to gravitational perturbation by an unknown planet.
In fact Neptune could have been discovered without the mathematical arguments. It very nearly was discovered by Galileo, the first person who could possibly have discovered a new planet. Galileo turned his telescope on the planets and was immediately fascinated by the system of Jupiter and its moons which he observed.