Traditional and molecular cytogenetics.

Traditional cytogenetic methods have relied on tissue culture techniques to generate adequate mitotic cells for the analysis of chromosome disorders for prenatal diagnosis. Chromosome banding techniques allow the evaluation of mitotic cells for structural and numerical aberrations and define the nature of any rearrangement. With the advent of fluorescent in situ hybridization methodology, which combines the molecular technologies of chromosome-specific probes and in situ molecular hybridization, it has become possible to analyze chromosomal numerical and structural aberrations from interphase cells. The use of molecular cytogenetic techniques should greatly increase the speed and diagnostic resolution of clinical specimens.     

Prenatal diagnosis: molecular genetics and cytogenetics

The technologies developed for the Human Genome Project, the recent surge of available DNA sequences resulting from it and the increasing pace of gene discoveries and characterization have all contributed to new technical platforms that have enhanced the spectrum of disorders that can be diagnosed prenatally. The importance of determining the disease-causing mutation or the informativeness of linked genetic markers before embarking upon a DNA-based prenatal diagnosis is, however, still emphasized. Different fluorescence in situ hybridization (FISH) technologies provide increased resolution for the elucidation of structural chromosome abnormalities that cannot be resolved by more conventional cytogenetic analyses, including microdeletion syndromes, cryptic or subtle duplications and translocations, complex rearrangements involving many chromosomes, and marker chromosomes. Interphase FISH and the quantitative fluorescence polymerase chain reaction are efficient tools for the rapid prenatal diagnosis of selected aneuploidies, the latter being considered to be most cost-effective if analyses are performed on a large scale. There is some debate surrounding whether this approach should be employed as an adjunct to karyotyping or whether it should be used as a stand-alone test in selected groups of women.     

Cytogenetics of aborters and abortuses

783 aborters and 430 abortuses were studied in a prospective cytogenetic survey which attempted to link chromosome abnormalities and history of recurrent abortion. 425 female and 358 male spontaneous aborters and their 430 abortuses (310 were karotyped) showed 4 women and 2 men as balanced translocation carriers (3 Robertsonian and 3 reciprocal translocations) and a woman with an XXX karotype. 5 of the abortuses were successfully karotyped; 4 had inherited unbalanced translocation products, and the other had a balanced 13q14q translocation plus trisomy 18. Apparently, translocation chromosomes carried by aborters were transmitted to their abortuses. Structural chromosome abnormalities were found with higher frequency (.8%) among aborters than among the general adult population (.3%). Translocation carriers were more frequent among the aborters with histories of recurrent abortions (2.7%) as well as among aborters with a history of perinatal deaths (3.6%) than among those persons with no such histories (.6%). Data on 18 couples whose 2 or 3 successive spontaneous abortuses were karotyped are presented.     

Cytogenetics of recurrent abortions

Chromosome banding studies were carried out on both partners of 37 couples who had had two or more spontaneous abortions. Three patients had chromosome disorders; one was a triple-X female and the other two (one male and one female) were t(13;14) translocation carriers. Review of the literature indicates that the over-all frequency of major chromosome disorders in couples with repeated abortions is 2.6%. About three-fourths of these disorders are reciprocal and Robersonian translocations.     

Cytogenetics of human spermatozoa

Human sperm chromosomes can be visualized after their fusion with zona-free hamster eggs. We analyzed a total of 867 metaphases from 33 men that had been classified into three different groups. We present a detailed summary of the kind and frequency of chromosome aberrations we encountered. A comparison of our results with previous studies demonstrates considerable variations in numerical and structural chromosome anomalies in spermatozoa from normal, healthy men. The possible reasons for this are discussed. We reviewed some factors which are supposed to correlate with the occurrence of sperm chromosome aberrations; the effect of paternal age is still uncertain.     

光谱核型分析技术在细胞遗传中的应用

G显带核型分析技术是细胞遗传工作中的常规显带技术。然而其不能发现小的或复杂的染色体异常。而光谱核型分析技术则使人类24种染色体同时染色,仅通过1次实验就可直观、快速地观察所有染色体。其能够发现隐匿性及复杂的染色体异常、能确定标记染色体的来源及其他不明来源的衍生染色体,因而成为常规染色体核型分析技术的有益补充。近年结合G显带、荧光原位杂交(FISH)技术,光谱核型分析技术已应用于诊断复杂性染色体异常以及确定标记染色体的来源,亦可用于检测未受精卵细胞非整倍体。综述该技术在细胞遗传工作中的应用。     

2269例细胞遗传学研究

总结Ｔ２２６９例的细胞遗传学资料，发现染色体异常３１０例，总异常率为１３，６６％。各组中智力低下的染色体异常率最高，占４４．４４％，大多为２１三体；男、女生殖缺陷的染色体异常率次之，分别为２７．７８％和３５．８１％，主要为性染色体异常；流产及异常生育史的染色体异常率最低，分别为４，１４％和１．１０％，主要为常染色体平衡易位。提示细胞遗传学检查对上述疾病的早期诊断和早期治疗有重要意义。     

Cytogenetics of uncleaved oocytes and arrested zygotes in IVF programs

Purpose: Cytogenetic studies of arrested oocytes and zygotes were used to understand in vitro fertilization (IVF) failures. Methods: We investigated the cytogenetics (Giemsa banding and FISH) of 710 uncleaved oocytes and 94 arrested zygotes from 208 patients undergoing IVF procedures. Results and Conclusions: Of uncleaved oocytes without a polar body, 39% were judged cytogenetically abnormal (17% unbalanced predivision and 21.5% diploid). Of 575 oocytes with a polar body, 124 (21.5%) showed numerical or structural chromosome aberrations. In arrested zygotes, approximately equal cases were found with separate condensed haploid complements (no syngamy), nuclear asynchrony and pulverized DNA, and apparently cytogenetically normal zygotes arrested at mitosis. These data on chromosome abnormalities were also analyzed with respect to two ovarian stimulation protocols and to maternal age. Both ovarian stimulation protocols showed the same levels of chromosome abnormalities. Overall chromosome abnormalities and premature chromosome condensation were also unchanged with maternal age. These data illustrate the significance of chromosome aberrations in IVF failures.Presented at the 5th Annual Meeting of the International Working Group on Preimplantation Genetics, Hamburg, Germany, June 28, 1995.