Loss of heterozygosity (LOH) in a cell represents the loss of normal function of one allele of a gene in which the other allele was already inactivated. This term is mostly used in the context of oncogenesis; after an inactivating mutation in one allele of a tumor suppressor gene occurs in the parent's germline cell, it is passed on to the zygote resulting in an offspring that is heterozygous for that allele. In oncology, loss of heterozygosity occurs when the remaining functional allele in a somatic cell of the offspring becomes inactivated by mutation. This results in no normal tumor suppressor being produced and this could result in tumorigenesis.