(AC)n dinucleotide repeat polymorphism in 5' beta-globin gene in native and Mestizo Mexican populations.

Repeated sequences are dispersed along the human genome. These sequences are useful as markers in diagnosis of inherited diseases, in forensic medicine, and in tracking the origin and evolution of human populations. The (AC)n repeated element is the most frequent in the human genome. In this paper, the (AC)n repeated element located in the 5' flanking region of the beta-globin gene was studied by single-strand conformation polymorphism (SSCP). Four ethnic Mexican groups (Mixteca, Nahua, Otomí, Purépecha) and a Mestizo population were analyzed. We observed three alleles, A [(AC)16, B [(AC)14], and C [(AC)18], with a frequency of between 68.2% and 86.9%, 13.1% and 18.2%, and 6.7% and 13.7%, respectively. Allele C was present only in Purépecha and Mestizo groups. The absence of this allele in the other ethnic groups studied suggests that there is low genetic admixture of Purépecha and that this is a relatively isolated population. However, it could be that the C allele occurs in low frequencies in the other groups as a result of small sample sizes. The (AC)n repeat polymorphism in the beta-globin gene has not been previously studied in Amerindian populations.

Blood groups and red cell acid phosphatase types in a Mixteca population resident in Mexico City.

Several blood groups, ABO, Rh, Ss, Fy, Jk, and red cell acid phosphatase (ACP) types were studied in a native Mixteca population that has resided in Mexico City since 1950. Gene frequencies were obtained and used to establish admixture estimates with blacks and whites. The subjects came from three different geographical areas: High Mixteca, Low Mixteca, and Coast Mixteca. All frequencies were in Hardy-Weinberg equilibrium. The difference in the ABO frequencies was statistically significant when subjects from the three areas were compared simultaneously. Rh frequencies differed only between the High and the Low Mixteca populations. The ACP frequencies were similar between the Low Mixteca population and a previously reported Mestizo population. However, there were significant differences between the High Mixteca group and a Mestizo population, all the subjects being from Oaxaca. This is the first report of Ss, Fy, Jk, and ACP frequencies in a Mixteca population. Am. J. Hum. Biol. 11:525-529, 1999. Copyright 1999 Wiley-Liss, Inc.

Molecular studies of Mendelian disorders, embryonic neoplasias, and polymorphisms in selected samples of the general population. A contribution to the genetic characterization of the Mexican population.

Molecular studies using polymerase chain reaction (PCR) and restriction enzymes, as well as intragenic STRs and newly designed primers, were performed in patients with Duchenne-Becker muscular dystrophy, sickle cell anemia, retinoblastoma, and nephroblastoma. The usefulness of these methodologies in the precise identification of mutational changes, in carrier detection and in the understanding of neoplastic transformations, as well as its applications in genetic counseling and prenatal diagnosis, are discussed. In addition, genetic polymorphisms in the beta globin gene cluster and in mtDNA were investigated. All these studies, the first performed in our population, contribute to establish the genetic origin and to a better characterization of the Mexican population.

Methods for the analysis of cellular kinetics in PHA-stimulated blood lymphocytes using BrdU incorporation. A comparative study.

The cellular cycle (cc) span was measured by using differential sister-chromatid staining (DSCS) and applying the following methods: cellular cycle time (cct) according to the graphic method of Dutrillaux and Fosse (G-cct); the analytical equation (A-cct) proposed in the present paper, and the average generation time (AGT) suggested by Ivett and Tice. The mean values obtained by the three methods were 12.5, 12.7, and 19.5 h, respectively. A-cct is the more precise method, since the equation of the analytical procedure allows the utilization of numerical data, and when the graphical method is used, the values plotted in a graph may vary according to the employed scale. Cct is the choice over AGT because the first evaluates actively dividing cells and only considers those at M2 or M3. It will be useful to study cell proliferation kinetics in genetic pathological conditions and to investigate with accuracy the effect of cytostatic and cytotoxic drugs.

[Polymorphisms of chromosomes 1, 9, and 16 in Mexican mestizos]. / Polimorfismos de los cromosomas 1, 9 y 16 en mestizos mexicanos.

The frequency of heterochromatic polymorphisms on C-banded chromosomes 1, 9 and 16 in two inter-racial Mexican populations was analyzed. Secondary constriction (qh) regions were classified according to a semi-quantitative procedure which showed to be simple and convenient. We compare our results with those in other populations.

[Cytogenetic study of the parents of 85 index cases with regular trisomy 21]. / Estudio citogenético en los progenitores de 85 casos índice con trisomía 21 regular.

The parents of 85 Down syndrome cases with regular 21 trisomy were studied cytogenetically. The lymphocyte chromosomes were stained with G-banding technique and 100 metaphases were analyzed in the father, the mother and the index case. Among the mothers two cases of mosaic 46, XX/47, XX, +21 (2.35%) were found and among the fathers no mosaic cases were found. Reciprocal and robertsonian translocations were not observed. In one of the fathers a pericentric inversion of the Y chromosome (0.61%) was found. The results are compared with those of similar studies and discussed in relation to genetic counseling and to the possible existence of an "interchromosomal effect" in man.

Utilidad de los heteromorfismos cromosómicos obtenidos por bandas G para la identificación de ilegitimidad / Usefulness of G chromosome banding for illegitimacy detection

Se investigó la utilidad de algunos heteromorfismos cromosómicos obtenidos por bandas G para identificar hijos ilegítimos. En 80 familias se estudiaron a ambos padres y a 171 de sus hijos, estableciéndose además la sensibilidad de los marcadores. Los resultados mostraron que de los 171 hijos uno (0.6//) era ilegítimo, cifra muy inferior a la obtenida con el uso de varios grupos sanguíneos y marcadores séricos que fue de 6.7 por ciento en un grupo similar de familias. Se pudo demostrar que el bajo índice de detección de ilegitimidad de los heteromorfismos cromosómicos se explica, parcialmente cuando menos, por la baja sensibilidad de los mismos la cual fue de 27 por ciento en comparación con una sensibilidad de 60 por ciento encontrada con los otros marcadores genéticos

[Usefulness of chromosomal heteromorphisms obtained by G-banding for identification of illegitimacy]. / Utilidad de los heteromorfismos cromosómicos obtenidos por bandas G para la identificación de ilegitimidad.

The present paper investigates the use of G-bands chromosome heteromorphisms for illegitimacy testing. We studied both parents and 171 of their children in 80 families utilizing the material, in addition, to establish the procedures sensitivity. The results showed that one (0.6%) of the 171 children studied was illegitimate, which was much lower than the figure of 6.7% obtained in a similar population studied with three blood group systems and three serum genetic markers. We could show that the low efficiency of the G-band heteromorphisms is at least partially due to its low sensitivity, 27% as compared to 60% obtained with the other genetic markers.

Chromosome abnormalities and sister chromatid exchanges in children with acute intoxication due to inhalation of volatile substances.

Deliberate inhalation of volatile substances is a common and harmful practice among young persons worldwide. Recently, we described chromosome damage in children who chronically inhale volatile agents. Clinical and cytogenetic studies were performed for 15 "sniffing" children (13 boys and 2 girls), the purpose of which was to define the chromosomal effect of the acute intoxication. A significant increase in the rate of chromosome abnormalities and in the frequency of sister chromatid exchanges (SCEs) was found in sniffers vs. controls. The values were also higher in children who were acutely intoxicated than in those who chronically inhaled volatile agents. Clinical, socioeconomic, and cytogenetic findings are also discussed.

Sindrome de Down e ilegitimidad / Ilegitimacy and Dow syndrome

Por medio de seis marcadores genéticos cuya sensibilidad había sido establecida previamente se determinó la frecuencia de ilegitimidad en una población de 44 familias que tenían en común ser del Distrito Federal y tener un hijo con síndrome de Down por trisomía regular. Se encontraron siete hijos ilegítimos, dos con síndrome de Down y cinco entre los hermanos de los casos índice, lo que representa una frecuencia de 11.1 por ciento. Esa frecuencia es cuatro veces superior a la encontrada por otros autores en una población de la ciudad de Mexíco. A pesar de ese elevado índice de ilegitimidad los hallazgos no apoyan, cuando menos de manera directa, la hipótesis de que en los niños con síndrome de Down se encuentra una mayor frecuencia de ilegitimidad. El análisis de las frecuencias génicas permite establecer que no existe segregación preferencial de alguno de los marcadores en el síndrome de Down y que los sujetos estudiados se encuentran en equilibrio de Hardy- Weinberg

Gene frequencies and admixture estimates in a Mexico City population.

Five hundred and ten students of the Universidad Nacional Autónoma de México were tested to determine the distribution of ABO, MN, Rr-Hr blood groups, and serum haptoglobin, albumin, and Factor Bf types. Based on the results we found that the proportion of Indian and White genes are of 56.16 and 43.84%, respectively in the dihybrid model and 2.93, 56.22, and 40.85% for Blacks, Indians, and Whites in the trihybrid one. The present study reveals a higher proportion of Indian genes in the Mexico City population than estimated in previous publications. Reasons why the present results apply to a much larger group of Mexico City mestizos than the previous ones are given.

A patient with 44 chromosomes.

A patient with Turner syndrome and a 13q14q translocation is described. Not a single such case had been reported. The principal findings in connection with double aneuploidy in humans are discussed.

Experiencia de un laboratorio privado de citogenetica medica. / Experience at a private laboratory of medical cytogenetic

En un lapso de aproximadamente 15 anos se estudiaron desde el punto de vista citogenetico y para fines de diagnostico a 677 casos indice y a 38 pacientes de los mismos en un laboratorio privado de citogenetica medica. Se encontro anormalidad cromosomica en el 31.6 por ciento de los propositi. En el 76.8 por ciento de los casos la anormalidad era autosomica y gonosomica en el 23.2 por ciento. Los resultados se comparan con los obtenidos en dos hospitales de atencion medica a tercer nivel de la ciudad de Mexico

Trisomy iop. A report of two cases due to a familial translocation rcp (10;21) (pII;pII).

Trisomy for the short arm of chromosome number 10 was diagnosed (by a G-banding method) in two sisters with multiple congenital defects. Their mother and two other sisters showed a balanced translocation 46,XX rcp(10;21)(p11;p11), so the affected girls were the result of a maternal adjacent-1 meiotic segregation with a karyotype 46,XX, der(21), rcp(10;21)(p11;p11)mat. The concordant features in the abnormal patients constitute the following syndrome: severe psychomotor retardation, congenital microsomatia, mild hydrocephalus with cranium-face disproportion, low set ears with hypoplastic helix, ocular colobomata, pulmonary stenosis,flexion deformity of wrists and elbows, bilateral fifth finger clinodactyly and simian creases, hypoplastic dermal ridges, bilateral talipes, persistent icterus and delayed bone age. The phenotypical and cytogenetic findings permit the individualization of the 10p trisomy.