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No / Chemotherapy drugs usually inflict a lethal dose to tumour cells with the consequence that these cells are being killed by cell death. However, each round of chemotherapy also causes damage to normal somatic cells. The DNA cross-linking agent oxaliplatin which causes DNA double-strand breaks and vinflunine which disrupts the mitotic spindle are two of these chemotherapy drugs which were evaluated in vitro using peripheral lymphocytes from colorectal cancer patients and healthy individuals to determine any differential response. Endpoints examined included micronucleus (MN) induction using the cytokinesis-blocked micronucleus (CBMN) assay and pancentromeric fluorescence in situ hybridisation. Also, survivin expression was monitored since it regulates the mitotic spindle checkpoint and inhibits apoptosis. Oxaliplatin produced cytogenetic damage (MN in binucleated cells) via its clastogenic but also previously unknown aneugenic action, possibly through interfering with topoisomerase II, whilst vinflunine produced MN in mononucleated cells because of incomplete karyokinesis. Survivin expression was found to be significantly reduced in a concentration-dependent manner by not only oxaliplatin but surprisingly also vinflunine. This resulted in large numbers of multinucleated cells found with the CBMN assay. As survivin is upregulated in cancers, eliminating apoptosis inhibition might provide a more targeted chemotherapy approach; particularly, when considering vinflunine, which only affects cycling cells by inhibiting their mitotic spindle, and alongside possibly other pro-apoptotic compounds. Hence, these newly found properties vinflunine – the inhibition of survivin expression - might demonstrate a promising chemotherapeutic approach as vinflunine induces less DNA damage in normal somatic cells compared to other chemotherapeutic compounds. / Saudi Arabian Government

While age-related sex chromosomal aneuploidy is a well-characterized phenomenon, the relationship between autosomal loss and age remains unclear. The emergence of the specific and highly sensitive fluorescence in situ hybridization (FISH) technology has enabled investigators to study interphase cells, thereby overcoming problems inherent with the study of metaphase spreads for acquired aneuploidy assessment. Despite all the advantages of this technique, there are some limitations that could be misleading when scoring interphase autosomal aneuploidy. In this study we show that sex chromosomal hypoploidy is correlated with age. By using a twin study design, we evaluated Y chromosome hypoploidy frequencies and found that loss of the Y chromosome is likely to be a multifactorial phenotype, being influenced by both genetic and environmental factors. An analysis of acquired aneuploidy frequencies for 13 autosomes in men showed that only one autosome, chromosome 3, had an age-related increase in acquired aberrations levels. Using a multi-probe study design, we determined that an apparent loss of fluorescent signal(s) could result from the coincident positioning (overlaying) of the repeat sequences targeted by the probes (due to either somatic homolog pairing or aggregation of the heterochromatic regions). Therefore, caution should be taken when performing autosomal FISH analysis to avoid overestimation of autosomal aneuploidy in uncultured leukocytes.

Brain gliomas represent a heterogeneous group of tumors of various histological subtypes which differ according to their response to treatment and prognosis. Tumors created from astrocytes and oligodendrocytes occur most often. Histological classification of gliomas is often subjective, as well as their treatment today is still problematic. The aim of this diploma thesis was to carry out a detailed molecular cytogenetic analysis of the genome of tumor cells in patients with histologically confirmed brain gliomas of different subtypes and stages of malignancy, look for recurrent aberration-specific subtypes and assess their potential role in the development and progression of cancer. To observation specific frequency known aberrations in different subtypes of brain tumors, we used the method of interphase FISH (I-FISH) with a panel of specific locus and / or centromeric DNA probes. The whole genome analysis and detection of cryptic unbalanced changes in the genome of tumor cells, we used the method of SNP array. Combining methods I- FISH and SNP array was detected not only the known chromosomal changes that are typical of the different subtypes of tumors, but also new or uncommon recurrent aberrations. In patients with low-grade gliomas are the most commonly observed acquired UPD (aUPD) on the short...

Les carcinomes urothéliaux représentent la 4ème cause de cancer chez l'homme après les cancers de la prostate, du colon et du poumon. Leur incidence est en augmentation de plus de 50% depuis 25 ans. Ce cancer présente principalement deux formes, une superficielle (70% des cas) de bon pronostic et une invasive (30%) de mauvais pronostic. Les formes superficielles nécessitent une surveillance active rapprochée afin d'identifier les récidives fréquentes et l'évolution vers un stade invasif. Cette surveillance fait principalement appel à la cystoscopie et engendre morbidité et cout importants. Une alternative à la cystoscopie est possible à l'aide de tests de détection urinaire des cellules cancéreuses, mais leur sensibilité jusqu'à présent n'est pas suffisante pour une utilisation en pratique courante. Notre but a été de développer un outil de détection urinaire des tumeurs urothéliales.Matériel, Méthode et RésultatsLes tumeurs urothéliales étant très instables sur le plan génétique, le travail a initialement consisté à faire la synthèse des anomalies cytogénétiques retrouvées dans la littérature. Les anomalies les plus pertinentes ont été sélectionnées et une puce de CGH en a été développée comprenant 341 clones (BAC) répartis sur l'ensemble des chromosomes. Cette puce intitulée BCA-1 a été développée en collaboration avec la société ArrayGenomics (Voisins Le Bretonneux, France). La validité de ce test a été confirmée sur 10 lignées cellulaires tumorales et bénignes.Notre travail a ensuite consisté à étudier la valeur ajoutée de cette puce en pratique clinique. Pour ce faire, une cohorte de 163 patients porteurs de tumeurs urothéliales et de témoins a été constituée. Les urines ont été prélevées et analysées en utilisant la puce BCA-1. Un logiciel a été développé sous filemaker pro afin de permettre une saisie uniforme et détaillée des données cliniques et de prendre en considération le caractère complexe de la prise en charge de ces tumeurs.Le test urinaire utilisant la puce de CGH a montré une excellente performance diagnostique avec une sensibilité de 96% et une spécificité de 98% dans les tumeurs vésicale, et une sensibilité de 100% tumeurs du haut appareil urinaire.Enfin, le test a aussi permit de caractériser le caractère agressif ou non agressif des tumeurs sur le plan cytogénétique. Cette caractérisation est fortement corrélée avec le stade anatomopathologique et un troisième aspect de notre travail a montré que la détermination cytogénétique de l'agressivité des tumeurs prédisait l'évolution défavorable des tumeurs du haut appareil urinaire. Notre travail a permis le développement et l'analyse d'un nouveau test de dépistage urinaire des tumeurs urothéliales permettant le diagnostic urinaire de ces tumeurs et la caractérisation de leur caractère agressif éventuel, ainsi que le développement d'un logiciel de saisie et d'analyse des données cliniques. / Urothelial carcinomas are the 4th cause of cancer in men, following prostate, colon and lung cancer. An increase of 50% in its incidence was observed on the last 25 years. This cancer presents two types, a superficial type (70% of the cases) of good prognosis and an invasive type (30% of the cases) of bad prognosis. Superficial type require an active monitoring to identify recurrences and evolution to an invasive stage. This follow up is performed using cystoscopy and leads to some level of morbidity and a high cost. An alternative to cystoscopy is possible using urine test to detect cancer cells, but they are lacking of sensitivity to be used instead of cystoscopy in clinical practice. Our goal was to develop a urine detection tool of urothélial carcinomas.Material and MethodsUrothelial carcinoma usually present with a high level of genetic instability. We first analyse literature so to identify most relevant cytogenetic abnormalities that occur in urothélial carcinomas. A CGH array chip was designed using 341 clones (BAC) that were selected according to initial analysis. This chip called BCA-1 covers the whole genome and was developed in collaboration with ArrayGenomics (Voisins Le Bretonneux, France).ResultsThis test has shown a good efficacy on a preliminary study of cytogenetic analysis on 10 cancerous and benign bladder cell lines. The Chip was then assessed in clinical practice on a series of 163 patients diagnosed with or without urothelial cancer. Urines were collected and analysed using the BCA-1 chip. A software was designed to favour homogeneous and detailed clinical data collection and take into consideration the complex management of the tumours.The test using the CGH chip as shown an excellent diagnosis performance with a sensitivity of 96% and a specificity of 98% for bladder cancer detection, and a sensitivity of 100% on upper urinary tract detection.Finaly, the test was able to define the grade of the tumour according to cytogenetic loci affected. This grade was strongly correlated with the pathology score and could be used to predict outcomes in upper urinary tract carcinomas. Our work lead to the developpement and the analysis of a new urothélial carcinoma urinary detection test, to the identification of the agressivity of the tumour, and to the development of an analysis and data entry software for clinical details.

Title.: Utilisation of molecular cytogenetic techniques in reproductive genetics Chromosomal abnormalities constitute one of the most important causes of birth defects, fertilization failure and/or human infertility. Approximately, 40-50% of human conceptuses are chromosomally abnormal, 6% of the abortions during the first trimester of gestation are directly linked to chromosomal abnormality, while at term 0.6% of livebirths present with such features. Most of these abnormalities originate from the gametogenesis and arise through disturbed meiotic processes. Each gamete is a final and original product of the meiosis carrying a unique chromosomal set. Therefore, cytogenetic examination of individual gametes represents an important scientific challenge for our undrstandidng of the formation, incidence and etiology of aforementioned chromosomal abnormalities. Nonetheless, it is very technically demanding to perform efficient chromosomal investigation on gametes, hence single cells. My Ph.D. thesis is focused on the development of new techniques for the detection of chromosomal abnormalities in gametes and embryos. We developed a PNA-based technique as an alternative to conventional FISH and PRINS-based methods for fast, efficient and robust in situ detection of chromosomal abnormalities in human...

Em estudos etiológicos sobre a deficiência mental (DM), as anomalias cromossômicas, tanto numéricas quanto estruturais, são fatores que apresentam frequência relativa significante. O objetivo deste trabalho foi estudar as frequências e os tipos de anomalias cromossômicas em afetados por DM nas APAEs (Associação de Pais e Amigos dos Deficientes) de Batatais, Altinópolis e Serrana, objetivando conhecer melhor a contribuição destas anomalias na DM nessa região, caracterizando os tipos e as freqüências das aberrações cromossômicas observadas e compará-las entre as APAEs. Pacientes com suspeita de anomalias cromossômicas foram selecionados para o estudo. O critério usado para a seleção da amostra foi a realização do cariótipo em todos os afetados por DM com anomalias estruturais maiores e/ou menores. A análise citogenética foi feita através de cultura de linfócitos do sangue periférico e a coloração utilizada foi banda G, sendo analisadas 20 metáfases por paciente. Dos 505 indivíduos avaliados nas três APAES, 265 realizaram estudo citogenético, sendo encontradas 61 alterações cromossômicas (12,1% do total e 23,0% dos selecionados para cariótipo). Na APAE de Batatais, dos 305 indivíduos avaliados, 174 realizaram cariótipo, sendo encontradas 33 (10,8% do total) anomalias cromossômicas. Em Altinópolis, dos 107 indivíduos avaliados, 54 realizaram cariótipo, sendo observados 16 cariótipos anômalos (14,9% do total). Na APAE de Serrana, dos 93 indivíduos avaliados, 37 realizaram cariótipo, sendo encontradas 12 (12,9% do total) anomalias cromossômicas. Esses resultados demonstram que anomalias cromossômicas contribuem significativamente para a etiologia da DM e que a citogenética clássica possui importantes implicações na prática médica para o diagnóstico dos indivíduos afetados, assim como, para o aconselhamento genético das famílias. Além disso, observa-se que a APAE de Batatais, por apresentar uma porcentagem menor de indivíduos afetados por DM grave, 60,7%, possui uma menor incidência de anomalias cromossômicas quando comparada as APAEs de Altinópolis e Serrana que apresentam uma frequência de 87,8% e 83,9% de indivíduos com DM grave, respectivamente, indicando que alterações cromossômicas são mais frequentes em indivíduos afetados por DM grave. / In etiological studies on mental retardation (MR), the chromosomal abnormalities, both numerical and structural, are factors that have significant relative frequencies. The objective was to study the frequencies and types of chromosomal abnormalities in patients affected by MR in APAEs (Associação de Pais e Amigos dos Deficientes) of Batatais, Altinópolis and Serrana. This aims to better understand the contribution of these abnormalities to MR in these regions, and thus characterizing the types and frequencies of chromosomal aberrations observed in order to compare them between APAEs. Patients suspected of chromosomal abnormalities were selected for the study. The criterion used for sample selection was the achievement of the karyotype of all patients affected by MR with major and/or minor structural abnormalities. Cytogenetic analysis was performed on cultures of peripheral blood lymphocytes, where the band G was used for staining. Twenty metaphases were analyzed per patient. Of the 505 individuals evaluated in three APAEs, a cytogenetic study was performed on 265 patients, and 61 chromosomal abnormalities were found (12.1% of the total and 23.0% of the selected karyotypes). In APAE of Batatais, karyotypes were performed on 174 of the 305 subjects studied, and we found 33 chromosomal abnormalities (10.8% of total). In Altinópolis, 54 karyotypes were performed out of the 107 subjects studied, and we observed 16 abnormal karyotypes (14.9% of total). In APAE Serrana, 37 karyotypes were performed out of the 93 subjects studied, and 12 chromosomal abnormalities (12.9% of total) were found. These results show that chromosomal abnormalities contribute significantly to the etiology of MR and that classical cytogenetics have important implications in medical practice for diagnosis of affected individuals as well as for genetic counseling of the families. Moreover, it is noted that in the APAE of Batatais, because of the smaller percentage of individuals affected by severe MR, 60.7% have a lower incidence of chromosomal abnormalities when compared to the APAEs of Altinópolis and Serrana which have frequencies of 87.8% and 83.9% of individuals with severe MR, respectively. This indicates that chromosomal abnormalities are more frequent in individuals affected by severe MR.

A tirbo Oryzomyini é a mais especiosa dentre os sigmodontíneos e os estudos citogenéticos nesses roedores refletem tal diversidade exibindo uma gama excepcional de variabilidade cromossômica. O número diploide varia de 2n = 16 até 2n = 88, além disso, algumas espécies apresentam polimorfismos de cromossomos autossômicos e sexuais, assim como a presença de supernumerários. De modo a compreender melhor a variabilidade cromossômica do grupo, o presente trabalho tem como objetivo: fazer uma revisão citogenética da tribo; descrever sete novos cariótipos (Euryoryzomys sp. 2N = 58/FN = 92, Neacomys sp. 1 2N = 48/FN = 54, Neacomys sp. 2 2N = 54/FN = 62, Oecomys sp. 1 2N = 54/FN = 84, Oecomys sp. 2 2N = 64/FN = 92, Oecomys sp. 3 2N = 84/FN = 110 e Scolomys sp. 2N = 62/FN = 80); realizar um estudo de pintura cromossômica utilizando sondas cromossomo-específicas de todo o complemento cromossômico de Holochilus sciureus e alguns autossomos de Oligoryzomys moojeni em quinze espécies de Oryzomyini (Cerradomys vivoi 2n = 50, Euryoryzomys sp. 2N = 58, Holochilus sciureus 2n = 56+2Bs, Hylaeamys megacephalus 2n = 54, Neacomys spinosus 2n = 64, Neacomys sp. 1 2n = 48, Neacomys sp.2 2n = 54, Nectomys rattus 2n = 52+1B, Nectomys squamipes 2n = 56+2Bs, Oecomys sp. 1 2n = 54, Oecomys sp. 2 2n = 64, Oligoryzomys moogeni 2n = 70, Pseudoryzomys simplex 2n = 56, Scolomys sp. 2N = 62 e Sooretamys angouya 2n = 58+2Bs); e por fim fazer uma análise filogenética da tribo baseada em dados de pintura cromossômica. Os resultados mostraram uma intensa reorganização genômica envolvendo inversões pericêntricas e/ou reposicionamento centromérico, inversões paracêntricas, rearranjos Robertsonianos, fusões e/ou fissões em tandem e translocações envolvidas na diversidade e evolução cromossômica de Oryzomyini. A utilização de duas abordagens diferentes na análise filogenética mostrou qual é mais confiável e apresenta resultados similares aqueles resultantes das análises morfológicas e moleculares. Além disso, os cromossomos sexuais dessas espécies apresentaram regiões homólogas compartilhadas entre todas as espécies analisadas com amplificação espécie-específica de heterocromatina / Oryzomyini is the most specious tribe of Sigmodontinae subfamily and cytogenetic studies of these rodents reflect such diversity displaying an exceptional range of karyotype variability. Diploid number vary from 2n = 16 to 2n = 88, in addition, some species present autosomal and sex chromosomes polymorphisms, besides the presence of B chromosomes. In order to understand the actual karyotype variability of Oryzomyini we present: a cytogenetic review of the tribe in order to rescue all chromosomal data available for the group; the description of seven new karyotypes (Euryoryzomys sp. 2N = 58/FN = 92, Neacomys sp. 1 2N = 48/FN = 54, Neacomys sp. 2 2N = 54/FN = 62, Oecomys sp. 1 2N = 54/FN = 84, Oecomys sp. 2 2N = 64/FN = 92, Oecomys sp. 3 2N = 84/FN = 110, and Scolomys sp. 2N = 62/FN = 80); a genome-wide comparative study using whole chromosome probes of the entirely chromosome set of Holochilus sciureus and some autosomes of Oligoryzomys moojeni in metaphases of fifteen Oryzomyini species (Cerradomys vivoi 2n = 50, Euryoryzomys sp. 2N = 58, Holochilus sciureus 2n = 56+2Bs, Hylaeamys megacephalus 2n = 54, Neacomys spinosus 2n = 64, Neacomys sp. 1 2n = 48, Neacomys sp.2 2n = 54, Nectomys rattus 2n = 52+1B, Nectomys squamipes 2n = 56+2Bs, Oecomys sp. 1 2n = 54, Oecomys sp. 2 2n = 64, Oligoryzomys moogeni 2n = 70, Pseudoryzomys simplex 2n = 56, Scolomys sp. 2N = 62, and Sooretamys angouya 2n = 58+2Bs) and; a phylogenetic analysis of Oryzomyini using chromosome painting data. The results showed an extensive chromosomal rearrangement, such as pericentric inversions or centromeric shift, paracentric inversions, Robertsonian rearrangements, tandem fusions/fissions, and translocations involved in the karyotype diversity and evolution of Oryzomyini. The use of two different approaches to perform a phylogenetic analysis based on chromosome painting data revealed which one is more trustworthy and present results more similar with molecular and morphological analysis. In addiction, the sex chromosomes of these species present homologous regions between all analysed species with amplification of species-specific heterochromatin

Este estudo representa a primeira avaliação ovariana, imunológica e hormonal realizada em duas espécies de felinos brasileiros ameaçados: L. pardalis (n=5) e L. tigrinus (n=4), antes e após 4 a 6 tratamentos alternados com as gonadotrofinas exógenas eCG/hCG e pFSH/pLH. Os animais foram submetidos a superovulação alternada com eCG-hCG e pFSH-pLH a cada quatro meses pelo período de dois anos, perfazendo um total de 6 intervenções. Os oócitos foram recuperados por vídeo laparoscopia, caracterizados quanto à morfologia e utilizados para determinação dos estágios do ciclo meiótico por análise citogenética e maturação pela caracterização de metáfase II. Avaliação ultra-estrutural por microscopia eletrônica de transmissão e varredura foi realizada para caracterização da morfologia dos oócitos. Antes e após cada intervenção sangue foi colhido e utilizado em análises hormonais séricas (progesterona e estradiol) por RIE e pesquisa de anticorpos para gonadotrofinas exógenas por ELISA. Comparando os tratamentos, não houve diferença significativa (p>0,05) no número total de estruturas ovarianas observadas em superovulações alternadas sucessivas, nas duas espécies estudadas. Também não houve diferença significativa em relação ao total de estruturas ovarianas encontradas em cada tratamento (5,7±1,2 eCG/hCG; 7,9±0,9 pFSH/pLH) para L. pardalis e (eCG/hCG 2,6±0,7; pFSH/pLH 2,0±0,5) para L. tigrinus. Embora L. pardalis tenham apresentado maior número de estruturas ovarianas por estimulação que L. tigrinus (p<0,05), a porcentagem de oócitos maduros em relação aos oócitos totais não diferiu, indicando que a metodologia utilizada foi eficiente. L. pardalis apresentaram maior número de oócitos totais e maduros nos tratamentos com pFSH/pLH (p<0,05), sendo que em L. tigrinus ambos tratamentos se comportaram de maneira semelhante (p>0,05). Não foi possível a caracterização dos estágios do ciclo meiótico pela avaliação da configuração cromossômica nos oócitos, sendo que nenhum oócito apresentou-se em metáfase II. Ultraestruturalmente os oócitos apresentaram características semelhantes aos observados em mamíferos de maneira geral. Dosagens hormonais séricas demonstraram um aumento de estradiol após as superovulações. Elevações de progesterona foram observadas em alguns momentos pré e pós superovulações. Embora alguns animais tenham demonstrado desenvolvimento de títulos para imunoglobulinas anti-gonadotrofinas exógenas, essa resposta imune humoral não parece interferir com a indução da atividade ovariana produzida pela superovulação, já que os animais responderam bem aos tratamentos alternados. Com estes resultados podemos concluir que essas espécies podem ser manejadas intensivamente usando tratamentos alternados com gonadotrofinas exógenas para procedimentos de reprodução assistida sem comprometer a resposta ovariana a esses hormônios. / This study represents the first assessment of ovarian, immunological and hormonal responses of two endangered Brazilian felids: L. pardalis (n=5) and L. tigrinus (n=4), treated with two exogenous gonadotropin regimens eCG/hCG and pFSH/pLH. Females were treated with four to six times alternating eCG/hCG and pFSH/pLH protocols using an interval of four months between each treatment. Ovarian follicular development and oocytes recovery were performed through laparoscopy. Recovered oocytes were submitted to the cytogenetical analysis and to the electron microscopy in order to evaluate the maturation (metaphase II) and the morphological and ultrastructural status, respectively. Blood samples were collected before each treatment and during the laparoscopy in order to measure progesterone and estradiol by RIA and to evaluate the immunological response to the exogenous gonadotropins by ELISA. Our results suggest that L. pardalis and L. tigrinus do not show a decrease (p>0.05) in ovarian response after repeated and alternate exposure to different gonadotropin treatments. In both L. pardalis and L. tigrinus, no differences were found regarding to the number of total ovarian structures (p>0.05) during successive gonadotropin treatments. When comparing the eCG/hCG and the pFSH/pLH treatments, there were no differences (p>0.05) regarding to the total number of ovarian structures in L. pardalis (5.7 ± 1.2 and 7.9 ± 0.9, respectively) or L. tigrinus (2.6 ± 0.7 and 2.0 ± 0.5, respectively). Despite the fact that the L. pardalis showed a higher number of follicles and CLs per stimulation (p<0.05) when compared to the L. tigrinus, no differences were found when analyzing the percentage of mature oocytes (p>0.05). Within species, both gonadotropin regimens were equally effective (p>0.05) to induce the follicular growth. No decreases (p>0.05) on the total number of ovarian structures and on the oocyte maturation percentages were observed between the sequential stimulations, but. L. pardalis showed a higher number of mature and total oocytes when treated with pFSH/pLH (p<0.05). L. Tigrinus didn’t show any differences regarding to the number of total and mature oocytes (p>0.05) when comparing both gonadotropin regimens. No oocytes in metaphase II were observed in the cytogenetic analyses. Oocytes histological evaluation showed that morphological characteristics were the same observed in others mammals. Hormonal analyses showed increased estradiol levels after superovulations. Higher levels of progesterone were observed before and after superovulations. Although some of these cats do demonstrate the development of anti-gonadotropin immunoglobulin titers, these humoral immune responses do not appear to interfere with gonadotropininduced ovarian stimulation. In this study, animals treated repeatedly with alternating regimens of eCG/hCG and pFSH/pLH showed no decrease in total ovarian structures after four to six successive treatments. These findings are potentially valuable for the ongoing efforts to develop and apply assisted reproductive technologies to the management and conservation of endangered felid populations.

INTRODUÇÃO: As aberrações cromossômicas constituem uma das maiores categorias das doenças genéticas, e são causa significativa do retardo mental e das malformações congênitas. Essas anormalidades correspondem a 50% dos casos de abortos espontâneos, 6% de natimortos e 0,6-1% de nativivos. OBJETIVO: Avaliar a freqüência das aberrações cromossômicas e classificar as principais aberrações encontradas nos pacientes atendidos em um serviço de Genética. CASUÍSTICA E MÉTODOS: Estudo retrospectivo de registros de resultados dos cariótipos de pacientes atendidos no Instituto da Criança no período 1992-2002. RESULTADOS: A freqüência de aberrações cromossômicas nos pacientes foi de 22% em 1122 cariótipos. As alterações numéricas foram 70,8% e 29,2% estruturais. A síndrome de Down foi a aberração numérica mais encontrada em 117/247 (47,4%) pacientes, e a segunda foi a síndrome de Edwards, em 18/247 (7,3%), seguida pela síndrome de Patau, que ocorreu em 9/247 (3,6%) pacientes. Entre as aberrações sexuais, a síndrome de Turner foi a mais freqüente, 18/247 (7,3%), seguida de três casos de triplo X, um de Klinefelter e um duplo Y. Dentre as aberrações estruturais, as deleções destacaram-se, com 27/247 (10,9%) dos casos; houve nove casos de síndrome de \"Cri-du-chat\" e oito de Wolf-Hirschhorn. CONCLUSÃO: A freqüência significativa de aberrações cromossômicas encontradas salienta como fundamental o uso do cariótipo de rotina nos pacientes atendidos no serviço de Genética, para definição diagnóstica e aconselhamento genético aos pacientes e seus familiares. / INTRODUCTION: Chromosomal disorders are included among the most important causes of genetic diseases with mental retardation and congenital malformation. Fifty percent of these abnormalities are spontaneously aborted and affect at least 6,0% of the stillbirth and the frequency in live births is 0.6%-1%. OBJECTIVE: To assess the frequency and the main of chromosomal disorders in patients assisted at a genetic service. CASUISTIC AND METHODS: A retrospective study was carried out regarding the record karyotype of patients assisted at Instituto da Criança within the period of 1992-2002. RESULTS: The frequency of chromosomal disorders of the patients was found in 22.0% among 1122 karyotypes. The numerical abnormalities among patients were 70.8% and 29.2% of them were structurals. Down syndrome was the most common numerical abnormality, found in 117/247 (47.4%) patients, followed by Edwards syndrome in 18/247 (7.3%) and Patau syndrome in 9/247 (3.6%) patients. Among the sexual abnormalities, Turner syndrome was the most common, in 18/247 (7.3%) patients, followed by three cases of triple X syndrome, one case of Klinefelter syndrome and a case of XYY syndrome. Among all structural abnormalities, the deletions were the most common, found in 27/247 (10.9%) of the cases, with 9 patients with \"Cri-du-chat\" syndrome and 8 cases of Wolf-Hirschhorn syndrome. CONCLUSION: The significance frequency of chromosome abnormalities emphasizes the importance of the G-banding karyotyping in the routine evaluation of patients assisted at the genetic service to attain a diagnosis definition and provide genetic counseling to the patients and family members.