Monosomy

Monosomy is a form of aneuploidy with the presence of only one chromosome from a pair.

[1] Partial monosomy occurs when a portion of one chromosome in a pair is missing.

Human conditions due to monosomy: 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%.

[2] This bias may be due to the complexity of meiosis in oogenesis and the extremely prolonged arrest during meiosis that is prone to errors.

[3] However, in embryos that have developed to the cleavage stage, an equal maternal, paternal contribution to monosomies is observed.

Schematic karyogram of a human, showing the normal diploid karyotype. It shows annotated bands and sub-bands as used for the nomenclature of chromosome abnormalities including partial monosomies. It shows 22 homologous chromosomes , both the female (XX) and male (XY) versions of the sex chromosome (bottom right), as well as the mitochondrial genome (to scale at bottom left).
Further information: Karyotype