Dictionary of Human Evolution and Biology

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Loss Of Heterozygosity

1. the los of one of a pair of homologous chromatids, resulting in aneuploidy (2N 45) and hemizygosity for the chromatid.

2. the spontaneous, apparent conversion of all of the loci on an entire chromatid to the identity of the opposite homologous allele, resulting in homozygosity at every locus; this is thought to be due to trisomy followed by the los of the uniparental isochromatid (see disomy).

3. the apparent conversion of a single locus or small region of a chromatid by methylation and parental imprinting. Loss of heterozygosity is a feature of several forms of cancer.

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