Molecular Cytogenetic Classification of Down Syndrome and Screening of Somatic Aneuploidy in Mothers (original) (raw)
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Cytogenetic Analysis in Down Syndrome
Int J Hum …, 2010
Clinically diagnosed Down syndrome cases are referred for karyotyping and counseling. Data on incidence patterns of the 3 cytogenetic types of Down syndrome from the cases seen during the duration of 35 years is presented. Chromosomes were examined after G-banded technique of peripheral lymphocyte cultures. For each patient, in addition to the detailed case history in the proforma 15 metaphases were examined and in cases of mosaicism, the count was increased to 25 to 50 metaphases for analysis. A total of 874 cases were confirmed to have the karyotype of Down syndrome. 509 were male probands (58.24%) and 365 (41.76%) were female cases. The most common was free trisomy 21 in 759 (86.9%), translocation in 77 (8.8%) and mosaicism in 38 (4.3%) cases. Robertsonian translocation 14;21 (48;62.34%) was prevalent among the 77 cases with translocation and the remaining 29 cases had the translocation of chromosome 21 either to chromosomes 1 (1) or 15(2) or 21 (26). The sex ratio has indicated the prevalence of the males for the total sample (1.41:1) (509: 365) as well as for the 3 basic cytogenetic types of DS. Included in the male trisomy 21 are the 2 cases with Klinefelter syndrome (KFS)(48,XXY+21) and one with de novo Robertsonian translocation between chromosomes 13 and 14.
Cytogenetic findings at Down syndrome and their correlation with clinical findings
Bosnian journal of basic medical sciences / Udruženje basičnih mediciniskih znanosti = Association of Basic Medical Sciences, 2005
Down syndrome is a genetic state characterized by trisomy of chromosome 21. In the retrospective study for 12 years period (1991-2002) we have conducted correlation between cytogenetics analyses and clinical findings in our centre at 96 male and 83 female patients. Down syndrome was confirmed by cytogenetics analyses in 84 (87.5%) male patients and excluded in 12 (12.5%) male patients. Down syndrome was confirmed by cytogenetics analyses in 71 (85.5%) female patients and excluded in 12 (14.5%) female patients. Most common karyotype is free trisomy found in 139 (89.7%) examinees, than follows translocation form determined in 9 (5.8%), and mosaicism determined in 7 (4.5%) examinees. Our results indicate that cytogenetics analyses are necessary to confirm diagnosis of Down syndrome.
Cytogenetic Analysis of Down Syndrome
Objective: Down syndrome is a common genetic disease, diagnosed with congenital malformation/mental retardation. Down syndrome occurs in all races & economic levels. It is caused by third copy of chromosome 21, there are there forms of DS. Simple Trisomy 21, Translocation Trisomy and Mosaic Trisomy. The aim of the study is to know cause of Down syndrome. Chromosomal analysis was carried out by G banding technique. Materials and Methods: 1 ml of peripheral blood samples were collected in Out Patient Department of pediatrics and Cytogenetic analysis was performed. Results: Out of 28, 3 female cases, 2 male cases were Down syndrome, All the 5 cases were free trisomy 21, which is common type of Down syndrome; we have not identified Robertsonian translocation and mosaic type of DS.
Cytogenetic abnormalities and clinical presentation in down syndrome patients
IP innovative publication pvt ltd, 2020
Total 60 samples were received for karyotyping from patients of developmental delay, dysmorphism and mental retardation, of which 20 cases showed trisomy 21. There was an equal incidence in males and females. All neonates (20%) showed broad short neck and decreased muscle tone at birth. Most common feature in infants (50%) was depressed nasal bridge and slanting eyes. All children (30%) presented with developmental delay and mental retardation. Low set ears and depressed nasal bridge (80%) was the most common finding across all age groups. Most common CHD was VSD (20%). Robertsonian translocation involving 14q and 21q was seen in 15 % cases. One case presented with transient abnormal myelopoiesis at birth. One case presented with additional balanced t(10;18)
Chromosome 21 and Down syndrome: from genomics to pathophysiology
Nature Reviews Genetics, 2004
Genomic aneuploidy, defined as an abnormal number of copies of a genomic region, is a common cause of human genetic disorders. Classically, the term aneuploidy was restricted to the presence of supernumerary copies of whole chromosomes (trisomy), or absence of chromosomes (monosomy), but we extend this definition to include deletions or duplications of subchromosomal regions. Trisomy 21 is a model of all human disorders that are the result of supernumerary copies of a genomic region. In this review, we focus on Down syndrome (DS) and human chromosome 21 (HSA21) to show the effect that genomics has had on our understanding of the 'disorders of the genome'. We discuss the recent advances in genome sequencing, comparative genome analysis, functional genome exploration, use of model organisms and lessons from models of gene overexpression. We also discuss the consequences of genomic dosage imbalance owing to an extra copy of a genomic segment (trisomy). These are exciting times for genomic disorders, such as trisomy 21, because we now have the necessary tools to understand how three copies of a functional genomic element result in abnormal phenotypes. Trisomies According to the size of the triplicated genomic region, trisomies can be divided into four categories: complete, or whole-chromosome, trisomies; partial trisomies; microtrisomies and triplication of single genes or single functional genomic elements. Whole-chromosome trisomies. Whole-chromosome trisomies that result from meiotic or mitotic non-disjunction events are common in humans; they account for 0.3-0.5% of live births. Trisomy for HSA21, which results in Down syndrome and occurs at ~1 in 750 live births, is the most frequent event. Trisomies are often observed in a significant proportion of spontaneous abortions; for example, trisomy 16 is found in 1 out of 13, and trisomy 21 in 1 out of 43 such abortions 1. Partial trisomies. Partial (or segmental) trisomies that involve a genomic region of more than one chromosomal band (usually larger than 5 Mb) are much less frequent than whole-chromosome trisomies. They usually result from abnormal meiosis and segregation in individuals with balanced chromosomal rearrangements. One in about 1,800 newborns have an unbalanced, non-robertsonian rearrangement and approximately half of these are partial trisomies. Unbalanced ROBERTSONIAN TRANSLOCATIONS with trisomies of the long arms of ACROCENTRIC CHROMOSOMES occur in 1 of about 14,000 newborns 1. Microtrisomies. This type of trisomy is defined here as the partial trisomy of a genomic segment that is shorter
Journal of medical genetics, 1999
The population risk for trisomy 21 is 1 in 700 births but some couples are at a much higher risk owing to parental translocation or mosaicism. We report on the first attempt to carry out preimplantation genetic diagnosis for two such couples using cleavage stage embryo biopsy and dual colour FISH analysis. Each couple underwent two treatment cycles. Couple 1 (suspected gonadal mosaicism for trisomy 21) had two embryos normal for chromosome 21 transferred, but no pregnancy resulted; 64% (7/11) unfertilised oocytes/embryos showed chromosome 21 aneuploidy. Couple 2 (46,XX,t(6;21)(q13;q22.3)) had a single embryo transferred resulting in a biochemical pregnancy; 91% (10/11) oocytes/embryos showed chromosome 21 imbalance, most resulting from 3:1 segregation of this translocation at gametogenesis. The opportunity to test embryos before implantation enables the outcome of female meiosis to be studied for the first time and the recurrence risk for a Down syndrome pregnancy to be assessed.
A First Cytogenetic Study of Down Syndrome in Albania
International Journal of Science and Research (IJSR)
Down syndrome (DS) also known as trisomy 21 is a genetic complex disorder and the most common and best known autosomal chromosome abnormality in humans. Even though the majority of cases of DS can be identified based on clinical findings, cytogenetic analysis is essential to confirm the diagnosis and to provide information for genetic counseling. The present study is the first national consecutive series of Down Syndrome in Albanian population during the period 1984-2015. This study allowed the frequency of three basic cytogenetical types and the frequency of occurrence of the rarer karyotypes of Down syndrome to be estimated. Also the maternal age effect on the frequency of births of children with Down syndrome was evaluated. The frequency of occurrence of the different karyotypes was analyzed. The free trisomy 21 was the most common karyotype (nearly 91% of all cases). The ratio of mosaic trisomy 21 was 2.1%. The ratio of Robertsonian and reciprocal translocations were 5,7% and 0.2%, respectively. The chromosomal abnormalities (CAs) in addition to trisomy 21 were present in 0,8 % of all cases. Conclusions: Knowledge of the cytogenetic types are essential and carried out greatly helped in the management of these children and for counseling the affected families.
Prenatal Diagnosis, 2003
Rapid prenatal diagnosis of common chromosome aneuploidies have been successful through quantitative fluoresent PCR (QF-PCR) assays and small tandem repeat (STR) markers. The purpose of our study was to investigate the clinical feasibility for rapid prenatal detection of Down syndrome using the quantitative fluorescent PCR in uncultured amniocytes. DNA was extracted from uncultured amniotic fluid of normal karyotype (n=200) and of Down syndrome (n=21). It was amplified using QF-PCR with four STR markers located on chromosome 21. Among normal samples, the ranges of diallelic peaks for at least one STR marker were 1.0-1.3 for D21S11, 1.0-1.4 for D21S1411 and 1.0-1.5 for D21S1270. Down syndrome samples showed trisomic triallelic patterns or trisomic diallelic patterns. The sensitivity, specificity, and efficiency of the assay for detecting Down syndrome were 95.4%, 100%, and 99.5%, respectively. Rapid prenatal diagnosis of Down syndrome using QF-PCR is a reliable technique that aids clinical management of pregnancy.