Parental Origin of de novo chromosome abnormalities.

利用位于目标染色体上的限制性片段长度多态作为遗传标记，研究了从头染色体异常的亲本来源和形成机制。结果表明：(1)18三体起源于母体，母体第1次或第2次减数分裂不分离是18三体的优势机制，与前人对21三体的研究结果一致；(2)额外X染色体起源于母体；在所研究的4例XXXXX或XXXXY患者中，在母系第1次和第2次减数分裂中连续发生3次不分离，提示人类存在控制染色体分裂的基因。(3)在短暂性骨髓增殖性综合征(TMS)患者中，21三体的起源是由于减数分裂或有丝分裂不分离导致的21号染色体的重复，并且21号染色体的异形标记都是“AAB”型，这表明位于21号染色体上的基因是“脱体纯合子”。(4)除1例I(X)外，所有结构异常的起源都是父系的。支持先前的假设，即非罗伯逊结构异常的起源优先于父系。

Parental origin and mechanism of formation of de novo chromosome abnormalities were studied with the use of restriction fragment length polymorphisms located on target chromosomes as genetic markers. The following results were obtained:(1) The origin of trisomy 18 is of maternal; Nondisjunction at the maternal 1st or 2nd meiosis is the preferential mechanism for trisomy 18, consistent with the previous results for trisomy 21.(2) The origin of supernumerary X chromosomes is of maternal; Three successive nondisjunctions at the maternal 1st and 2nd meioses had occurred in all of four cases of XXXXX or XXXXY examined, suggesting the presence of the gene controlling chromosome division in humans.(3) The origin of trisomy 21 in patients with transient myeloproliferative syndrome (TMS) is the duplication of one chromosome 21 due to either meiotic or mitotic nondisjunction, and the heteromorphic markers of the chromosomes 21 are all an "aab" pattern, suggesting that the genes located on chromosomes 21 in TMS cells are "disomic homozygous".(4) The origin of all structural abnormalities examined are of paternal, except for one case of i(X), supporting the previous hypothesis that the origin of non-Robertsonian structural abnormality is preferentially of paternal.