Monosomy is a form of aneuploidy with the presence of only one chromosome from a pair. Partial monosomy occurs when a portion of one chromosome in a pair is missing.

Human monosomy

Human conditions due to monosomy:

In embryos

Analyses of the products of human miscarriages show that the majority of aneuploidies (trisomies or monosomies) in early developing embryos arise from errors occurring during maternal meiosis and that paternal meiotic errors contribute less than 10%. This bias may be due to the complexity of meiosis in oogenesis and the extremely prolonged arrest during meiosis that is prone to errors. However, in embryos that have developed to the cleavage stage, an equal maternal, paternal contribution to monosomies is observed.