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Results 1 - 10 of 1996
Results 1 - 10 of 1996.
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[en] Base substitution mutations are far more common in human males than in females, and the frequency increases with paternal age. Both can be accounted for by the greater number of pre-meiotic cell divisions in males, especially old ones. In contrast, small deletions do not show any important age effect and occur with approximately equal frequency in the two sexes. Mutations in most genes include both types, and the sex and paternal age effect depends on the proportion of the two types. A few traits, of which Apert Syndrome is best understood, are mutation hot spots with all the mutations occurring in one or two codons, usually at one nucleotide. They occur with very high frequency almost exclusively in males and the frequency increases rapidly with paternal age. It has been suggested that the mutant cells have a selective advantage in the male germ-line prior to meiosis. Evidence for this surprising, but important, hypothesis is discussed. A possible mechanism is the conversion of asymmetrical stem-cell divisions into symmetric ones. Some traits with complex etiology show a slight paternal age effect. There is also a short discussion of the high deleterious mutation rate and the role of sexual reproduction in reducing the consequent mutation load. (author)
Journal
Journal of Radiation Research; ISSN 0449-3060; 
; v. 47(suppl.B); p. B75-B82
; v. 47(suppl.B); p. B75-B82
No abstract available
Journal
Genetics and Molecular Biology; ISSN 1415-4757; ; v. 23(3,suppl.); p. 300
; v. 23(3,suppl.); p. 300
[en] Unstable mutations or amplification of triplets constitute a kind of genetic alteration discovered during the last decade. They had been found inside or near genes important for the normal neurological function of the human being. In some cases, the presence of the amplification causes the inactivation of the gene or the synthesis of a new product which functions different from the original protein. Some common characteristics of diseases caused by the amplification of triplets are that it affects the nervous system and are degenerative in nature. The expression of the manifestations varies according to age. Most of them show genetic anticipation in which the severity of the manifestations increases with each generation and appear at an earlier age. In most cases, the severity of the symptoms is correlated positively to the size of the amplification. The diagnosis of an affected individual in a family may indicate the presence of an altered gene in other relatives. These relatives may not present evident signs of the illness either because it is of late onset or because they carry premutations. The molecular diagnosis of these mutations is important to estimate the risk of developing the disease and/or of transmitting the illness to the descendants and to eliminate the fears of healthy relatives who have inherited normal copies of the gene. (Author)
[es]
Las mutaciones inestables o amplificacion de tripletas constituyen un tipo de alteracion genetica descubierto durante la ultima decada. En condiciones normales, regiones especificas de algunos genes estan constituidas por repeticiones de una tripleta de nucleotidos como por ejemplo CAG, CGG, etc. Este nuevo tipo de mutacion consiste en un aumento en la cantidad de repeticiones lo que causa una alteracion en la expresion de dichos genes. Se les llama inestables porque se ha observado que el tamano de la secuencia repetida varia cuando las celulas se dividen por meiosis o por mitosis. Esto tiene implicaciones sobre la herencia de la enfermedad y el consiguiente consejo genetico y explica, en alguna medida el caracter degenerativo de estas patologias. Se han encontrado estas mutaciones dentro o cerca de genes importantes para la funcion neurologica normal del ser humano. La presencia de la amplificacion puede causar la inactivacion del gen, alterar el transporte de los ARNm desde el nucleo al citoplasma o provocar la sintesis de un nuevo producto con funciones diferentes a la proteina original. Algunas caracteristicas comunes de las enfermedades causadas por estas mutaciones son que afectan el sistema nerviosos y son degenerativas. La expresion de las manifestaciones clinicas depende de la edad. En su mayoria presentan el fenomeno de anticipacion genetica, en el cual las manifestaciones clinicas son mas severas y se inician a edades mas tempranas a traves de las generaciones en una misma familia. La severidad de los sintomas correlacionan en la mayoria de los casos en forma positiva con la cantidad de repeticiones de la tripleta correspondiente. La aparicion de un individuo afectado en una familia puede indicar la presencia de familiares asintomaticos que porten el gen alterado, ya sea porque es de manifestacion tardia, o porque son portadores de premutaciones. El diagnostico molecular de estas mutaciones permite estimar el riesgo que tiene desarrollar el cuadro clinico, de procrear individuos afectados y eliminar los temores de los familiares sanos que han heredado copias normales del gen. (Author)Journal
Acta Medica Costarricense; ISSN 0001-6012; ; v. 41(2); p. 7-15
; v. 41(2); p. 7-15
No abstract available
Journal
[en] Cases of cranio-facial bone anomalies were observed in 40 cases of neurofibromatosis. The cranio-facial skeletal manifestations are numerous and varied. Radiographic investigation is important to confirm the diagnosis, when neurologic and cutaneous signs are absent. The diagnosis should be easily confirmed by a conventional radiographic study. (authors). 14 refs., 7 figs., 2 tabs
Journal
Annales de Radiologie Medecine Nucleaire - Revue d'Imagerie Medicale; ISSN 0003-4185; ; CODEN ANLRAT; v. 38(3); p. 139-144
; CODEN ANLRAT; v. 38(3); p. 139-144
[en] Chromosomal abnormalities are responsible for several congenital malformations in the world, some of these are associated to telomeric/subtelomeric deletions. The abnormalities involving the telomere of chromosome 12 are rare, with few reports of deletions involving 12q24.31 region in the literature, and, to our knowledge, only four of them in the 12q24.31-q24.33 region. We report a further case of interstitial deletion of bands 12q24.31-q24.33 associated with autism spectrum disorder. A 2-year-old boy with global developmental delay associated with multiple congenital anomalies. The Human Genome CGH Microarray 60K confirmed the diagnosis of 12q deletion syndrome. This study made a review of the current literature comparing our patient with previously reported cases. These detailed analyses contribute to the development of genotype/phenotype correlations for 12q deletions that will aid in better diagnosis and prognosis of this deletion. (author)
Journal
Einstein (Online); ISSN 2317-6385; ; v. 18(eRC5335); 5 p
; v. 18(eRC5335); 5 p
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