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Human cytogenetics. A current overview.

M M Cohen·L S Rosenblum-Vos·G Prabhakar
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Abstract

Chromosomal abnormalities are the basis for a substantial proportion of human morbidity and mortality. During the past 35 years, the field of human cytogenetics has helped to elucidate the etiology of many congenital malformation/mental retardation syndromes. Through adaptation of technological advances and integration of molecular biological techniques, cytogenetics continues to contribute significantly to our knowledge of clinical genetics, chromosomal fine structure and function, gene mapping, and prenatal diagnosis. This review outlines the basic concepts, recent findings, and current laboratory approaches to cytogenetic diagnosis.

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AmniocentesisChorionic Villi SamplingChromosome AberrationsChromosome DeletionChromosome DisordersChromosome MappingCordocentesisCytogeneticsDNAFetal DiseasesGene Expression RegulationHumansIn Situ Hybridization, FluorescenceKaryotypingNeoplasmsOncogenesPrenatal DiagnosisSyndromeJournal ArticleReview

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M M Cohen, L S Rosenblum-Vos, G Prabhakar. 1993. Human cytogenetics. A current overview.. https://doi.org/10.1001/archpedi.1993.02160350033005

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PubMed1999

Frequencies of chromosomal abnormalities at amniocentesis: over 20 years of cytogenetic analyses in one laboratory.

Prenatal diagnosis of chromosomal disorders has been performed for more than 20 years, mainly for advanced maternal age. Chromosomal abnormality rates derived from second trimester amniocentesis have mainly come from a collection of small-scale studies from North America and Western Europe. Accurate risk estimates for chromosomal abnormalities are important tools for the physician or obstetrician who would need to make referrals to a prenatal genetic center. This paper presents amniocentesis rates of clinically significant cytogenetic abnormalities for various indications, including advanced maternal age, previous chromosomal abnormality, parental structural rearrangement and a family history of aneuploidy as defined in the text. These data come from a Canadian prenatal diagnosis laboratory with more than 20 years experience in second trimester cytogenetic analysis. They show that the overall frequency of chromosomal abnormalities for advanced maternal age (> or = 35 years) is 1.79%. In this group, 21% of all abnormalities are structural rearrangements (including markers) and less than half of all abnormalities are trisomy 21. The advanced maternal age specific risk of aneuploidies at second trimester is 1.24%. Recurrence risk for aneuploidy after a previous one is 1.29%. However, it is much higher (4.84%) for women of > or = 35 years. When a parent's brother, sister, nephew or niece is affected, the risk of occurrence of aneuploidies (0.24%) is not elevated. When there is a balanced translocation in one of the parents, the overall risk is 10.2% for unbalanced translocations and 37.3% for balanced translocations.

Amniocentesis↗
PubMed1999

Comparison of cell cultures, chromosome quality and karyotypes obtained after chorionic villus sampling and early amniocentesis with filter technique.

548 cell cultures and karyotypes obtained by early amniocentesis with filtration technique (EAF) at a mean gestational age of 12 1/2 weeks were compared with 555 obtained by transabdominal chorionic villus sampling (CVS) at a mean gestational age of 11 weeks. The number of abnormal karyotypes, culture failure rate and harvest time were evaluated. The results were then compared with three similar studies from the literature evaluating early amniotic fluid cultures obtained with conventional techniques compared with chorionic villus cultures. Further, the quality of the chromosome preparations from chorionic villi and early amniotic fluid respectively was compared. More abnormal karyotypes were found among the CVS cultures, which was expected due to earlier sampling and presence of confined placental mosaicism. No ambiguous results were present after EAF. The lowest culture failure rate of 0.2 per cent was found after EAF compared with 0.9 per cent among CVS. EAF also showed a significantly lower culture failure rate when compared with the literature, where early amniocentesis (EA) had been carried out by standard techniques. The time from sampling to harvest was longer in the EAF group (mean 9.5 days) compared with CVS (mean 6.1 days), in accordance with the literature. Nevertheless, the culture time of EAF was significantly shorter than the mean of EA from the comparative studies, whereas CVS culture times showed no differences. Rates of pseudomosaicism, maternal cell contamination, single cell aberrations, number of chromosome bands, mitoses counted and number of primary cultures needed for each karyotype were also compared. We concluded that EAF carried out around 12 1/2 weeks of gestation is a successful method with a lower culture failure rate compared with CVS cultures from 11-week gestations and with a significantly lower culture failure rate when compared with EA from similar studies. EAF provides chromosome preparations of high quality, and the risk of ambiguous karyotypes is very low.

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