The loss of one allele at a specific locus, caused by a deletion mutation; or loss of a chromosome from a chromosome pair, resulting in abnormal HEMIZYGOSITY. It is detected when heterozygous markers for a locus appear monomorphic because one of the ALLELES was deleted.

Synonyms: Allelic Losses, Heterozygosity Loss, Allelic Loss, Loss of Heterozygosity, Heterozygosity, Loss of