carlos zapata - Academia.edu (original) (raw)
Papers by carlos zapata
Revista de la Facultad de Agronomía
La presencia de especies reactivas de oxígeno generan daños y estrés oxidativo, al haber producci... more La presencia de especies reactivas de oxígeno generan daños y estrés oxidativo, al haber producción y eliminación de estas especies en el organismo se presentan situaciones patológicas y de envejecimiento, estas especies pueden ser controladas mediante agentes reguladores como lo son sustancias antioxidantes de bajo peso molecular, lo cual conlleva a generar un protocolo de una metodología de evaluación antioxidante que sea fácilmente reproducible bajo las condiciones del laboratorio de análisis instrumental de la Universidad CES. ORAC es un método ampliamente utilizado para analizar la capacidad antioxidante, pero es un método altamente sensible y posee factores que puede presentar alteraciones si no se tienen estándares bien estipulados generando fluctuaciones en la lectura o proporcionando datos que no sean válidos. Por lo tanto, se estandarizará el método bajo los parámetros estipulados por las Buenas Prácticas de Fabricación (PAF), obteniendo resultados satisfactorios en términ...
Voltage stability determines the maximum loadability of a power system and power distribution fee... more Voltage stability determines the maximum loadability of a power system and power distribution feeder reconfiguration determines optimum feasible alternatives for load connection in order to increase service reliability. Although strongly connected, these analyses have been traditionally performed independently; thus, this paper presents a study on their relationship. The main result is the criterion of losses minimization applied in the reconfiguration analysis implicitly leads to the improvement of voltage stability but an explicit assessment of voltage stability allows the identification of reconfiguration alternatives that although are not optimum offer good loadability and stability.
This paper presents a methodology based on the sequential Montecarlo simulation technique for the... more This paper presents a methodology based on the sequential Montecarlo simulation technique for the reliability assessment of unbalanced power distribution systems.
Water, 2019
Estuaries are transitional environments with ideal conditions for port construction and navigatio... more Estuaries are transitional environments with ideal conditions for port construction and navigation. They represent a challenge to hydrographic services due to the dynamics of the seabed and the tidal wave deformation. The bottom slope, the convergence of the channels, and the nonlinear effects produced by the bottom friction produce variation in both the tidal range and the location of the chart datum (CD). In this study, sea level data series obtained from the nodes of the mesh of a hydrodynamic model (virtual tide gauges) were used to calculate the harmonic constituents, form factor, asymmetry, and estuary type. The final chart datum surface, obtained from the hydrodynamic model, was used to determine the separation values between zones and also the number of tidal zones in an estuarine system. It was found that in a complex hydrodynamics scenario, the use of the ellipsoidal referenced surveying (ERS) method is more convenient than traditional tidal zoning survey. In the ERS metho...
Revista Urología Colombiana / Colombian Urology Journal, 2019
Resumen Objetivo Determinar los factores asociados a la reestrechez uretral en pacientes llevados... more Resumen Objetivo Determinar los factores asociados a la reestrechez uretral en pacientes llevados a uretroplastia. Métodos Estudio observacional analítico retrospectivo. Se revisaron las historias clínicas de pacientes llevados a uretroplastia en el HSJ entre 2012-2017. Se realizó un análisis bivariado para estudiar las asociaciones entre la reestrechez uretral posterior a la uretroplastia y las caracteristicas preoperatorias, intraoperatorias y posoperatorias, así como un modelo de regresión logística múltiple. Resultados El total de pacientes llevados a uretroplastia fue de 82. La mediana de edad fue de 52 (RIQ = 35 -67) años. De todos los pacientes incluidos en el estudio 29 (36,2%) presentaron reestrechez. No se encontraron diferencias estadísticamente significativas en cuanto a los factores de riesgo en relación con reestrechez uretral en la población de estudio. Dentro de las técnicas quirúrgicas realizadas, los tipos de injerto utilizados en nuestros pacientes fueron la técni...
Journal of proteomics, Jan 29, 2018
Proteome changes derived from animals that have suffered pre-slaughter stress are a fact. In this... more Proteome changes derived from animals that have suffered pre-slaughter stress are a fact. In this study, Proteomic analysis was carried out on 20 bovine loin samples from Asturiana de los Valles and crossbreds cattle previously classified as normal and DFD meat at 24 h post-mortem using pH measurements. Sarcoplasmic sub-proteome of Longissimus thoracis at 24 h post-mortem was fractionated by the use of liquid isoelectric focusing (OFFGEL) in the pH range 3-10, followed by SDS-PAGE analysis of each retrieved fraction. The protein fractionation profile showed high reproducibility along the different sample groups. Five protein bands showed significant differences (p < 0.05) between the two groups, allowing discrimination between them. Proteins present in these bands, which were identified by LC-MS, were actin, phosphoglucomutase-1, alpha-crystallin B, heat shock protein beta-6 and heat shock protein beta-1. SIGNIFICANCE: The significance of this study relies on the optimization of ...
Journal of Agricultural and Food Chemistry, 2018
Patatin is the major tuber storage protein constituted by multiple isoforms highly variable acros... more Patatin is the major tuber storage protein constituted by multiple isoforms highly variable across potato (S. tuberosum) varieties. Here, we report a first association study of the variability of patatin isoforms between cultivars with their differences in tuber quality traits. Patatin-based proteomic distances were assessed between 15 table and/or processing potato cultivars from profiles of patatin obtained by two-dimensional electrophoresis. The content of ash, dry matter, reducing sugars, starch, total protein and amino acid composition was also evaluated in tubers of each cultivar. Results showed that proteomic distances were significantly (P < 0.05) associated with differences in the content of ash, dry matter and essential amino acids. Proteomic distances were also able to identify outlier cultivars regarding the content of dry matter, content of protein and protein quality. In conclusion, patatin-based proteomic distances can shorten the screening and selection processes of potato cultivars with advantageous characteristics in molecular breeding.
Langmuir : the ACS journal of surfaces and colloids, 2018
Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly impri... more Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations, and HPLC as well as MD simulations. Protected phenylalanines (Z-l/d-Phe) served as templates/analytes. While the influence of the counterion on the complex stability constants and anion-induced spectral changes shows a monotonous trend with increasing alkyl chain length at the prepolymerization stage, the cross-imprinting/rebinding studies showed a unique pattern that suggested the presence of adaptive cavities in the MIP matrix, related to the concept of induced fit of enzyme-substrate interaction. Larger cavities formed in th...
In this paper, a simulation of enlisting and use of free practicum courses for engineering studen... more In this paper, a simulation of enlisting and use of free practicum courses for engineering students from Instituto Tecnológico Metropolitano (ITM) is presented. Currently, this university is interested in getting better results to rank more competitively among other universities. Although the current courses are free, a high quality offer is evidently more expensive and we need to maximize the impact of the students in the labor market. In Colombia, many universities certify engineering students in computer sciences so, in order to attend the current needs of our institution and the labor market, we would like to contribute to decision-making processes through agent-based simulation regarding what Information Communications Technologies courses may fit best for the community and the industrial clusters ITM students are and will be working in.
Data in Brief, 2015
Proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress we... more Proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress were assessed on the basis of twodimensional electrophoresis (2-DE) data. In this study, the bootstrap resampling statistical technique and a new measure of relative change of the volume of 2-DE protein spots are shown to be more efficient than commonly used statistics to reliably quantify changes in protein abundance in stress response. The data are supplied in this article and are related to "Tackling proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress" by Franco et al. [1].
Gastroenterología y Hepatología, 2010
Molecular Biotechnology, 2002
Journal of Experimental Marine Biology and Ecology, 1990
The blue mussel Mytilus edulis L. and its southern relative, M. galloprovincialir Lmk., are two f... more The blue mussel Mytilus edulis L. and its southern relative, M. galloprovincialir Lmk., are two forms of mussel that live and are cultivated on the coasts of Europe. Up to date, the type or types of mussel that exist on the Atlantic coast of the Iberian Peninsula have not been clearly determined even though the N.W. comer of this region (Galician Rias) has the highest mussel production in the world. Diagnostic morphological characters (length of anterior adductor muscle scar and size and shape of the hinge plate) and diagnostic enzyme-gene polymorphisms (esterase-D, ieucine aminopeptidase-1, octopine dehydrogenase and mannose phosphate Lsomerase) for M. edul& and M. gai~oprovincial~ were investigated in samples of mussel populations (wild and cultivated) collected from N.W. Iberian Peninsula coastal sites. Evidence from both morphological variation and enzyme polymorphisms indicates that iU. gaZlopro~ncja2~ commonly occurs on the N.W. Iberian Peninsula. On the other hand, no evidence for the occurrence of M. edulir was found. The results are discussed in relation to the geographical dist~bution of both types of Myt#as on European coasts.
Human Heredity, 1997
We investigate properties of simple linkage disequilibrium mapping for five measures in the prese... more We investigate properties of simple linkage disequilibrium mapping for five measures in the presence of mutation at the marker and/or the disease locus and of initial incomplete linkage disequilibrium. In contrast to the stimulation approach that Devlin and Risch used, we calculate the expected values of various linkage disequilibrium measures under different assumptions based on a framework for linkage disequilibrium mapping. These expected values clearly demonstrate the expected performance of these measures. We find that the impact of marker mutation on their performance depends on the magnitude of the mutation relative to the proximity of the marker (i.e. recombination fraction between the marker and the disease locus). In the presence of recurrent mutation at the marker and/or disease locus, the performance of all measures, including the robust one, depends on the marker allele frequency. The initial incomplete linkage disequilibrium could render all measures useless. These expected values also show clearly why in Devlin and Risch's simulation some measures performed very badly under certain circumstances.
Human Heredity, 2011
Background/Objective: The analysis of linkage disequilibrium is relevant for the exploration of t... more Background/Objective: The analysis of linkage disequilibrium is relevant for the exploration of the structure and evolution of genomes and for the gene mapping of quantitative characters and human diseases. The strength of linkage disequilibrium between diallelic loci is commonly measured by the coefficients D′ and r. Recent studies suggest that r is more useful than D′ as a general measure of the strength of disequilibrium because it provides much more precise (lower sampling variance) and accurate (lower bias) estimates of disequilibrium. We compared for the first time the statistical properties of D′ and r taking into account their differences in range. Methods: The sampling properties of D′ and r were evaluated by simulation under a variety of realistic population conditions and varying sample sizes using standardised statistics that allow for comparisons of the precision, accuracy and efficiency of estimates with different ranges. Results: Simulations revealed that estimates of...
Heredity, 1995
A positive relationship between heterozygosity and growth rate, or less frequently, between heter... more A positive relationship between heterozygosity and growth rate, or less frequently, between heterozygosity and fitness components, has been found in many species. A particularly important component of net fitness is sexual selection. However, no studies have been made of the relationship between this character and multilocus heterozygosity in natural populations. In this study, a natural population of the intertidal flat periwinkle Littorina mariae was used to investigate the heterozygosity-sexual fitness relationship. A positive heterozygosity-sexual fitness relationship was found in male L. mariae, but not in females. The selective coefficients acting on the different heterozygosity classes of males ranged between 0.21 and 0.57 (average 0.39), and are similar to those found in previous studies on correlations between heterozygosity and other fitness components. This relationship accounted for approximately 1 per cent of the variance in matings. Furthermore, the contribution of each locus was associated with its homozygosity excess across loci. The positive heterozygosity-sexual fitness relationship showed the same characteristics as the heterozygosity-growth rate correlation. Finally, relationships between sexual selection and size of snail, and heterozygosity and size were found, although they did not account for the heterozygosity-sexual selection relationship.
Heredity, 1986
Experiments were conducted to analyse the pattern of mating and to look for sexual selection diff... more Experiments were conducted to analyse the pattern of mating and to look for sexual selection differences among karyotypes of Drosophila subobscura. This was done by assaying the mating structure of large experimental populations of this species set up with different frequencies of °ST and 034±7 chromosomal arrangements. From the experimental results, it is concluded that the mating pattern is at random and that the mating success of the male homokaryotypes °ST'°ST and 03÷4÷7/03÷4÷7, relative to that of the heterokaryotype °ST'°3+4+7, is frequencydependent favouring the rare male. These results are discussed in connection with the stable equilibrium attained in experimental population cages containing the °ST and 03÷47 chromosomal arrangements.
Heredity, 1995
The genetic structure of two sibling and sympatric species of the genus Littorina was compared us... more The genetic structure of two sibling and sympatric species of the genus Littorina was compared using allozymic loci. The two species are biologically and ecologically well-known and mostly show similar life history characteristics. Three populations of L. mariae Sacchi & Rastelli and L. obtusata (L.) were studied in the Muros-Noya Ria (Galicia, NW Spain). In addition, four microgeographical subsamples taken from one of the populations were analysed for each species. Age, sex and genotypes for nine polymorphic loci were studied in 1250 snails of both species. L. mariae showed larger genetic population subdivision and lower heterozygosity levels for the loci studied than did L. obtusata. Heterozygote deficiencies were found in only a few cases in natural populations of both species, usually affecting the Lap-i locus. No significant genetic differences among age or sex classes were found. These results may be explained by the lower effective population size in L. mciriae than in L. obtusata. Known differences between these species in generation interval and population density during the winter can cause the different effective population sizes suggested. These life history characteristics appear to provide the most likely explanations for the differences in genetic differentiation and heterozygosity between the two species. A previously unknown L. mariae morph from exposed shores is tentatively suggested to be conspecific.
Genetical Research, 1996
SummaryThe total gametic disequilibrium between two loci linked to polymorphic inversions can be ... more SummaryThe total gametic disequilibrium between two loci linked to polymorphic inversions can be partitioned into two types of components:withinandbetweenchromosome arrangements. The within components depend on the gametic disequilibrium within each chromosome arrangement. The between components depend on the locus-inversion disequilibria. This partitioning has practical applications and is indispensable for studying the dynamics of these systems because inversions greatly reduce recombination in the heterokaryotypes while allowing free, and sometimes different, recombination in each of the homokaryotypes. We provide equations for the per generation change of the various disequilibria for systems with two and three chromosome arrangements, and the general recursive equations predicting the disequilibria after any number of generations for the case of two arrangements. Simulation studies were carried out using different values of the recombination parameters and all possible initial ...
Evolution, 2000
Seasonal variation (spring, early summer, late summer, and autumn) of gametic disequilibrium betw... more Seasonal variation (spring, early summer, late summer, and autumn) of gametic disequilibrium between gene arrangements (OST and O3+4) of the O chromosome and Lap, Pept-1, and Acph allozyme loci, located inside these inversions, has been recorded in a natural population of Drosophila subobscura during seven years over a 15-year period. The length of the study allowed us to investigate the temporal variation of the allozyme-inversion associations by statistical methods of time series analysis. Cyclic seasonal changes of allozyme-inversion associations for both Lap and Pept-1 are detected in the natural population. In both cases, the patterns of seasonal change are due to the seasonal change of frequency of Lap and Pept-1 allozymes occurring exclusively within the OST gene arrangement. In contrast, the allozyme frequencies at these loci within the O3+4 gene arrangement are stable along seasons. The patterns of temporal variation of allozyme-inversion associations for Lap and Pept-1 in the natural population are contrasted with those previously published that correspond to gene arrangements of the O chromosome and nucleotide polymorphism at the rp49 region located inside these inversions, suggesting that natural selection is operating on these allozyme-inversion associations.
Revista de la Facultad de Agronomía
La presencia de especies reactivas de oxígeno generan daños y estrés oxidativo, al haber producci... more La presencia de especies reactivas de oxígeno generan daños y estrés oxidativo, al haber producción y eliminación de estas especies en el organismo se presentan situaciones patológicas y de envejecimiento, estas especies pueden ser controladas mediante agentes reguladores como lo son sustancias antioxidantes de bajo peso molecular, lo cual conlleva a generar un protocolo de una metodología de evaluación antioxidante que sea fácilmente reproducible bajo las condiciones del laboratorio de análisis instrumental de la Universidad CES. ORAC es un método ampliamente utilizado para analizar la capacidad antioxidante, pero es un método altamente sensible y posee factores que puede presentar alteraciones si no se tienen estándares bien estipulados generando fluctuaciones en la lectura o proporcionando datos que no sean válidos. Por lo tanto, se estandarizará el método bajo los parámetros estipulados por las Buenas Prácticas de Fabricación (PAF), obteniendo resultados satisfactorios en términ...
Voltage stability determines the maximum loadability of a power system and power distribution fee... more Voltage stability determines the maximum loadability of a power system and power distribution feeder reconfiguration determines optimum feasible alternatives for load connection in order to increase service reliability. Although strongly connected, these analyses have been traditionally performed independently; thus, this paper presents a study on their relationship. The main result is the criterion of losses minimization applied in the reconfiguration analysis implicitly leads to the improvement of voltage stability but an explicit assessment of voltage stability allows the identification of reconfiguration alternatives that although are not optimum offer good loadability and stability.
This paper presents a methodology based on the sequential Montecarlo simulation technique for the... more This paper presents a methodology based on the sequential Montecarlo simulation technique for the reliability assessment of unbalanced power distribution systems.
Water, 2019
Estuaries are transitional environments with ideal conditions for port construction and navigatio... more Estuaries are transitional environments with ideal conditions for port construction and navigation. They represent a challenge to hydrographic services due to the dynamics of the seabed and the tidal wave deformation. The bottom slope, the convergence of the channels, and the nonlinear effects produced by the bottom friction produce variation in both the tidal range and the location of the chart datum (CD). In this study, sea level data series obtained from the nodes of the mesh of a hydrodynamic model (virtual tide gauges) were used to calculate the harmonic constituents, form factor, asymmetry, and estuary type. The final chart datum surface, obtained from the hydrodynamic model, was used to determine the separation values between zones and also the number of tidal zones in an estuarine system. It was found that in a complex hydrodynamics scenario, the use of the ellipsoidal referenced surveying (ERS) method is more convenient than traditional tidal zoning survey. In the ERS metho...
Revista Urología Colombiana / Colombian Urology Journal, 2019
Resumen Objetivo Determinar los factores asociados a la reestrechez uretral en pacientes llevados... more Resumen Objetivo Determinar los factores asociados a la reestrechez uretral en pacientes llevados a uretroplastia. Métodos Estudio observacional analítico retrospectivo. Se revisaron las historias clínicas de pacientes llevados a uretroplastia en el HSJ entre 2012-2017. Se realizó un análisis bivariado para estudiar las asociaciones entre la reestrechez uretral posterior a la uretroplastia y las caracteristicas preoperatorias, intraoperatorias y posoperatorias, así como un modelo de regresión logística múltiple. Resultados El total de pacientes llevados a uretroplastia fue de 82. La mediana de edad fue de 52 (RIQ = 35 -67) años. De todos los pacientes incluidos en el estudio 29 (36,2%) presentaron reestrechez. No se encontraron diferencias estadísticamente significativas en cuanto a los factores de riesgo en relación con reestrechez uretral en la población de estudio. Dentro de las técnicas quirúrgicas realizadas, los tipos de injerto utilizados en nuestros pacientes fueron la técni...
Journal of proteomics, Jan 29, 2018
Proteome changes derived from animals that have suffered pre-slaughter stress are a fact. In this... more Proteome changes derived from animals that have suffered pre-slaughter stress are a fact. In this study, Proteomic analysis was carried out on 20 bovine loin samples from Asturiana de los Valles and crossbreds cattle previously classified as normal and DFD meat at 24 h post-mortem using pH measurements. Sarcoplasmic sub-proteome of Longissimus thoracis at 24 h post-mortem was fractionated by the use of liquid isoelectric focusing (OFFGEL) in the pH range 3-10, followed by SDS-PAGE analysis of each retrieved fraction. The protein fractionation profile showed high reproducibility along the different sample groups. Five protein bands showed significant differences (p < 0.05) between the two groups, allowing discrimination between them. Proteins present in these bands, which were identified by LC-MS, were actin, phosphoglucomutase-1, alpha-crystallin B, heat shock protein beta-6 and heat shock protein beta-1. SIGNIFICANCE: The significance of this study relies on the optimization of ...
Journal of Agricultural and Food Chemistry, 2018
Patatin is the major tuber storage protein constituted by multiple isoforms highly variable acros... more Patatin is the major tuber storage protein constituted by multiple isoforms highly variable across potato (S. tuberosum) varieties. Here, we report a first association study of the variability of patatin isoforms between cultivars with their differences in tuber quality traits. Patatin-based proteomic distances were assessed between 15 table and/or processing potato cultivars from profiles of patatin obtained by two-dimensional electrophoresis. The content of ash, dry matter, reducing sugars, starch, total protein and amino acid composition was also evaluated in tubers of each cultivar. Results showed that proteomic distances were significantly (P < 0.05) associated with differences in the content of ash, dry matter and essential amino acids. Proteomic distances were also able to identify outlier cultivars regarding the content of dry matter, content of protein and protein quality. In conclusion, patatin-based proteomic distances can shorten the screening and selection processes of potato cultivars with advantageous characteristics in molecular breeding.
Langmuir : the ACS journal of surfaces and colloids, 2018
Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly impri... more Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations, and HPLC as well as MD simulations. Protected phenylalanines (Z-l/d-Phe) served as templates/analytes. While the influence of the counterion on the complex stability constants and anion-induced spectral changes shows a monotonous trend with increasing alkyl chain length at the prepolymerization stage, the cross-imprinting/rebinding studies showed a unique pattern that suggested the presence of adaptive cavities in the MIP matrix, related to the concept of induced fit of enzyme-substrate interaction. Larger cavities formed in th...
In this paper, a simulation of enlisting and use of free practicum courses for engineering studen... more In this paper, a simulation of enlisting and use of free practicum courses for engineering students from Instituto Tecnológico Metropolitano (ITM) is presented. Currently, this university is interested in getting better results to rank more competitively among other universities. Although the current courses are free, a high quality offer is evidently more expensive and we need to maximize the impact of the students in the labor market. In Colombia, many universities certify engineering students in computer sciences so, in order to attend the current needs of our institution and the labor market, we would like to contribute to decision-making processes through agent-based simulation regarding what Information Communications Technologies courses may fit best for the community and the industrial clusters ITM students are and will be working in.
Data in Brief, 2015
Proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress we... more Proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress were assessed on the basis of twodimensional electrophoresis (2-DE) data. In this study, the bootstrap resampling statistical technique and a new measure of relative change of the volume of 2-DE protein spots are shown to be more efficient than commonly used statistics to reliably quantify changes in protein abundance in stress response. The data are supplied in this article and are related to "Tackling proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress" by Franco et al. [1].
Gastroenterología y Hepatología, 2010
Molecular Biotechnology, 2002
Journal of Experimental Marine Biology and Ecology, 1990
The blue mussel Mytilus edulis L. and its southern relative, M. galloprovincialir Lmk., are two f... more The blue mussel Mytilus edulis L. and its southern relative, M. galloprovincialir Lmk., are two forms of mussel that live and are cultivated on the coasts of Europe. Up to date, the type or types of mussel that exist on the Atlantic coast of the Iberian Peninsula have not been clearly determined even though the N.W. comer of this region (Galician Rias) has the highest mussel production in the world. Diagnostic morphological characters (length of anterior adductor muscle scar and size and shape of the hinge plate) and diagnostic enzyme-gene polymorphisms (esterase-D, ieucine aminopeptidase-1, octopine dehydrogenase and mannose phosphate Lsomerase) for M. edul& and M. gai~oprovincial~ were investigated in samples of mussel populations (wild and cultivated) collected from N.W. Iberian Peninsula coastal sites. Evidence from both morphological variation and enzyme polymorphisms indicates that iU. gaZlopro~ncja2~ commonly occurs on the N.W. Iberian Peninsula. On the other hand, no evidence for the occurrence of M. edulir was found. The results are discussed in relation to the geographical dist~bution of both types of Myt#as on European coasts.
Human Heredity, 1997
We investigate properties of simple linkage disequilibrium mapping for five measures in the prese... more We investigate properties of simple linkage disequilibrium mapping for five measures in the presence of mutation at the marker and/or the disease locus and of initial incomplete linkage disequilibrium. In contrast to the stimulation approach that Devlin and Risch used, we calculate the expected values of various linkage disequilibrium measures under different assumptions based on a framework for linkage disequilibrium mapping. These expected values clearly demonstrate the expected performance of these measures. We find that the impact of marker mutation on their performance depends on the magnitude of the mutation relative to the proximity of the marker (i.e. recombination fraction between the marker and the disease locus). In the presence of recurrent mutation at the marker and/or disease locus, the performance of all measures, including the robust one, depends on the marker allele frequency. The initial incomplete linkage disequilibrium could render all measures useless. These expected values also show clearly why in Devlin and Risch's simulation some measures performed very badly under certain circumstances.
Human Heredity, 2011
Background/Objective: The analysis of linkage disequilibrium is relevant for the exploration of t... more Background/Objective: The analysis of linkage disequilibrium is relevant for the exploration of the structure and evolution of genomes and for the gene mapping of quantitative characters and human diseases. The strength of linkage disequilibrium between diallelic loci is commonly measured by the coefficients D′ and r. Recent studies suggest that r is more useful than D′ as a general measure of the strength of disequilibrium because it provides much more precise (lower sampling variance) and accurate (lower bias) estimates of disequilibrium. We compared for the first time the statistical properties of D′ and r taking into account their differences in range. Methods: The sampling properties of D′ and r were evaluated by simulation under a variety of realistic population conditions and varying sample sizes using standardised statistics that allow for comparisons of the precision, accuracy and efficiency of estimates with different ranges. Results: Simulations revealed that estimates of...
Heredity, 1995
A positive relationship between heterozygosity and growth rate, or less frequently, between heter... more A positive relationship between heterozygosity and growth rate, or less frequently, between heterozygosity and fitness components, has been found in many species. A particularly important component of net fitness is sexual selection. However, no studies have been made of the relationship between this character and multilocus heterozygosity in natural populations. In this study, a natural population of the intertidal flat periwinkle Littorina mariae was used to investigate the heterozygosity-sexual fitness relationship. A positive heterozygosity-sexual fitness relationship was found in male L. mariae, but not in females. The selective coefficients acting on the different heterozygosity classes of males ranged between 0.21 and 0.57 (average 0.39), and are similar to those found in previous studies on correlations between heterozygosity and other fitness components. This relationship accounted for approximately 1 per cent of the variance in matings. Furthermore, the contribution of each locus was associated with its homozygosity excess across loci. The positive heterozygosity-sexual fitness relationship showed the same characteristics as the heterozygosity-growth rate correlation. Finally, relationships between sexual selection and size of snail, and heterozygosity and size were found, although they did not account for the heterozygosity-sexual selection relationship.
Heredity, 1986
Experiments were conducted to analyse the pattern of mating and to look for sexual selection diff... more Experiments were conducted to analyse the pattern of mating and to look for sexual selection differences among karyotypes of Drosophila subobscura. This was done by assaying the mating structure of large experimental populations of this species set up with different frequencies of °ST and 034±7 chromosomal arrangements. From the experimental results, it is concluded that the mating pattern is at random and that the mating success of the male homokaryotypes °ST'°ST and 03÷4÷7/03÷4÷7, relative to that of the heterokaryotype °ST'°3+4+7, is frequencydependent favouring the rare male. These results are discussed in connection with the stable equilibrium attained in experimental population cages containing the °ST and 03÷47 chromosomal arrangements.
Heredity, 1995
The genetic structure of two sibling and sympatric species of the genus Littorina was compared us... more The genetic structure of two sibling and sympatric species of the genus Littorina was compared using allozymic loci. The two species are biologically and ecologically well-known and mostly show similar life history characteristics. Three populations of L. mariae Sacchi & Rastelli and L. obtusata (L.) were studied in the Muros-Noya Ria (Galicia, NW Spain). In addition, four microgeographical subsamples taken from one of the populations were analysed for each species. Age, sex and genotypes for nine polymorphic loci were studied in 1250 snails of both species. L. mariae showed larger genetic population subdivision and lower heterozygosity levels for the loci studied than did L. obtusata. Heterozygote deficiencies were found in only a few cases in natural populations of both species, usually affecting the Lap-i locus. No significant genetic differences among age or sex classes were found. These results may be explained by the lower effective population size in L. mciriae than in L. obtusata. Known differences between these species in generation interval and population density during the winter can cause the different effective population sizes suggested. These life history characteristics appear to provide the most likely explanations for the differences in genetic differentiation and heterozygosity between the two species. A previously unknown L. mariae morph from exposed shores is tentatively suggested to be conspecific.
Genetical Research, 1996
SummaryThe total gametic disequilibrium between two loci linked to polymorphic inversions can be ... more SummaryThe total gametic disequilibrium between two loci linked to polymorphic inversions can be partitioned into two types of components:withinandbetweenchromosome arrangements. The within components depend on the gametic disequilibrium within each chromosome arrangement. The between components depend on the locus-inversion disequilibria. This partitioning has practical applications and is indispensable for studying the dynamics of these systems because inversions greatly reduce recombination in the heterokaryotypes while allowing free, and sometimes different, recombination in each of the homokaryotypes. We provide equations for the per generation change of the various disequilibria for systems with two and three chromosome arrangements, and the general recursive equations predicting the disequilibria after any number of generations for the case of two arrangements. Simulation studies were carried out using different values of the recombination parameters and all possible initial ...
Evolution, 2000
Seasonal variation (spring, early summer, late summer, and autumn) of gametic disequilibrium betw... more Seasonal variation (spring, early summer, late summer, and autumn) of gametic disequilibrium between gene arrangements (OST and O3+4) of the O chromosome and Lap, Pept-1, and Acph allozyme loci, located inside these inversions, has been recorded in a natural population of Drosophila subobscura during seven years over a 15-year period. The length of the study allowed us to investigate the temporal variation of the allozyme-inversion associations by statistical methods of time series analysis. Cyclic seasonal changes of allozyme-inversion associations for both Lap and Pept-1 are detected in the natural population. In both cases, the patterns of seasonal change are due to the seasonal change of frequency of Lap and Pept-1 allozymes occurring exclusively within the OST gene arrangement. In contrast, the allozyme frequencies at these loci within the O3+4 gene arrangement are stable along seasons. The patterns of temporal variation of allozyme-inversion associations for Lap and Pept-1 in the natural population are contrasted with those previously published that correspond to gene arrangements of the O chromosome and nucleotide polymorphism at the rp49 region located inside these inversions, suggesting that natural selection is operating on these allozyme-inversion associations.