Loss of heterozygosity

{
  "id": "MLC-T-ENV-016055",
  "term": "Loss of heterozygosity",
  "field": "Environment",
  "term_source": "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.\n\n2. 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.",
  "subject": "Biological substances",
  "references": [
    "National Cancer Institute Thesaurus",
    "NLM Medical Subject Headings (MeSH); National Cancer Institute Glossary"
  ],
  "url": "https://mlchart.com/terminology/environment/loss-of-heterozygosity/"
}