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Loss of Heterozygosity
Definition 1
A DNA sequence alteration process in which gain, loss, or exchange of DNA results in loss of function of one allele in a diploid cell. This term is most often used in the context of tumorigenesis, where a single copy of a tumor suppressor gene is sufficient to perform its function, and loss of the second copy may occur by a variety of DNA sequence rearrangements, resulting in bialleleic deficiency and permitting a step in the path to transformation. (NCI Thesaurus)
Definition 2
If there is one normal and one abnormal allele at a particular locus, as might be seen in an inherited autosomal dominant cancer susceptibility disorder, loss of the normal allele produces a locus with no normal function. When the loss of heterozygosity involves the normal allele, it creates a cell that is more likely to show malignant growth if the altered gene is a tumor suppressor gene. (NCI Dictionary)
Definition 3
The loss of one allele at a specific locus, caused by a deletion mutation; or loss of a chromosome from a chromosome pair. It is detected when heterozygous markers for a locus appear monomorphic because one of the alleles was deleted. When this occurs at a tumor suppressor gene locus where one of the alleles is already abnormal, it can result in neoplastic transformation. (NLM, Medical Subject Headings)
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