Asunto(s)
ADN Helicasas/genética , Queratosis , Esclerodermia Localizada , Neoplasias Cutáneas , Femenino , Humanos , Masculino , Linaje , Isoformas de ProteínasRESUMEN
Selection for higher and lower meiotic conversion frequencies was investigated in the fungus Ascobolus immersus. Strains carrying the same known gene conversion control factors, which have major effects on conversion frequencies at their specific target locus, sometimes gave significant differences in conversion frequency. Selection for high or low conversion frequencies at the w1-78 site was practiced for five generations, giving significant responses in both directions. These responses were due to polygenes, or genes of minor effect, not to new conversion control factors of major effect. Crosses of selected strains to strains with other mutations showed that the genes' effects were not specific to w1-78, but could affect conversion frequencies of another mutation, w1-3C1, at that locus and of two other loci, w-BHj and w9, which are unlinked to w1 or to each other. The proportional changes in gene conversion frequency due to selection varied according to the locus and site involved and according to the conversion control factor alleles present. There were differences of > or = 277% in conversion frequency between "high" and "low" strains. Selection for conversion frequency had little effect on other features of conversion, such as the frequency of postmeiotic segregation or the relative frequencies of conversion to mutant or wild type.
Asunto(s)
Ascomicetos/genética , Conversión Génica , Genes Fúngicos , Alelos , Cruzamientos Genéticos , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiología , Haploidia , Meiosis , Selección GenéticaRESUMEN
We present monozygotic twin boys with features of Kabuki syndrome. The twins were discordant for cleft palate and coarctation of the aorta. The occurrence of Kabuki syndrome in monozygotic twins has not been previously reported and reinforces the belief that this condition has a genetic basis. Chromosomal analysis on the boys showed a pseudodicentric chromosome 13 with an inactive centromere and satellite stalks at 13q12.11: 46,XY,psu dic(13)(13pter-->13q12.11::13p12-->13q11.00:: 13q12.11-->13qter). Their phenotypically normal mother appears to carry the same pseudodicentric chromosome 13.
Asunto(s)
Anomalías Múltiples/genética , Cromosomas Humanos Par 13/genética , Enfermedades en Gemelos/genética , Causas de Muerte , Línea Celular , Células Cultivadas , Centrómero/genética , Aberraciones Cromosómicas , Citogenética , Oído/anomalías , Anomalías del Ojo/genética , Cejas/anomalías , Cara/anomalías , Salud de la Familia , Femenino , Humanos , Lactante , Recién Nacido , Discapacidad Intelectual , Linfocitos/citología , Masculino , Linaje , Reacción en Cadena de la Polimerasa , Embarazo , Síndrome , Gemelos MonocigóticosRESUMEN
A quantitative treatment is given for meiotic gene conversion with its parameters and equations for their interactions to determine allele segregation class frequencies from heterozygotes. The possible pairing of both pairs of nonsister chromatids in a bivalent at exactly the same point is included. Using sets of data from Ascobolus immersus, it is shown that values for all nine parameters for hybrid DNA models of recombination can be obtained using an iterative computer program. The accuracy of the values is estimated and the double-strand gap repair model is considered. The parameter values obtained invalidate most of the simplifications used in previous quantitative analyses of gene conversion data. They showed total bias in strand preference in asymmetric hybrid DNA formation and some bias in which type of chromatid is the invading one. There were slight differences in repair frequency between the two types of mispair and very large differences in the direction of repair. Conversion control factors had major effects on hybrid DNA formation and repair of mispairs.