What term describes a missing chromosome in a diploid organism?

Monosomy refers to the condition where a diploid organism is missing one chromosome from its normal pair. In a typical diploid organism, chromosomes exist in pairs, with one chromosome inherited from each parent. If one of these chromosomes is absent, the organism is said to be monosomic for that specific chromosome.

Monosomy can lead to various developmental issues and genetic disorders because the loss of a chromosome can disrupt the balance of gene expression and affect the organism's overall phenotype. In contrast, the other terms relate to different chromosomal abnormalities: trisomy indicates an extra chromosome, euploidy refers to a complete set of chromosomes being present in a normal or balanced manner, and aneuploidy encompasses both monosomy and trisomy, indicating an abnormal number of chromosomes overall but not specifying whether a chromosome is missing or extra.