Engel E
Institut Universitaire de Génétique Médicale, Université de Genève, Switzerland.
Am J Med Genet. 1993 Jul 1;46(6):670-4. doi: 10.1002/ajmg.1320460613.
Uniparental disomy (UPD), the exceptional derivation of a pair of the offspring chromosomes from one parent only, may be compatible with normal or abnormal development and can result from gamete complementation, chromosome loss in trisomy, or duplication in monosomy (with or without residual mosaicism) and somatic recombination. In isodisomy, the uniparental pair is a duplicate of a same chromosome DNA template and causes an increased risk of recessive disorder by reduction to homozygosity. In heterodisomy, the pair remains heterozygous, made up of 2 non-recombinant homologous segments. But both iso- and heterodisomy may also cause disruption of the genomic imprints needed for differential expression of some maternal and paternal genes crucial to growth and development. Pure UPD preserves euploidy and, when harmful, is best regarded as a genomic qualitative imbalance by symmetrical excess and loss of parental homologous contribution affecting zygosity and imprint content. Instances of UPD reported till the spring 1992 are reviewed and their deleterious effects are described as they carried out lethality or morbidity by altering imprinting processes, mimicking deletions, generating recessive disorders, or prompting malignant cellular growth.
单亲二体性（UPD）是指一对子代染色体仅从一个亲本获得的异常情况，可能与正常或异常发育兼容，可由配子互补、三体中的染色体丢失、单体中的重复（有或无残留嵌合体）以及体细胞重组导致。在等二体性中，单亲染色体对是同一染色体DNA模板的重复，通过纯合化增加隐性疾病的风险。在异二体性中，染色体对保持杂合状态，由两个非重组同源片段组成。但等二体性和异二体性都可能导致一些对生长和发育至关重要的母源和父源基因差异表达所需的基因组印记破坏。纯合性单亲二体性保持整倍性，当有害时，最好将其视为基因组质量失衡，即亲本同源贡献的对称过量和缺失影响合子性和印记内容。本文回顾了截至1992年春季报道的单亲二体性实例，并描述了它们通过改变印记过程、模拟缺失、产生隐性疾病或促使恶性细胞生长而导致致死性或发病的有害影响。
