Monosomy is a form of aneuploidy with the presence of only one chromosome (instead of the typical two in humans) from a pair. Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.
Human conditions due to monosomy:
Turner syndrome - Women with Turner syndrome typically have one X chromosome instead of the usual two. Turner syndrome is the only full monosomy that is seen in humans.
Cri du chat syndrome -- (French for "cry of the cat" after the distinctive noise by affected persons' malformed larynx) a partial monosomy caused by a deletion of the end of the short p (from the word petit, French for small) arm of chromosome 5