Monosomy

• lacking one chromosome of a set; 2n - 1
  Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row
• Monosomy is the state of having a single copy of a chromosome pair instead of the usual two copies found in diploid cells. Monosomy can be partial if a portion of the second chromosome copy is present. Monosomy, or partial monosomy, is the cause of some human diseases such as Turner syndrome and Cri du Chat syndrome.