Estudios de parentesco mediante marcadores del ADN: Experiencia en resolución de casos en los últimos seis años / Kinship determination using DNA markers

Autosomal and Y chromosome short tandem repeats (STRs) and mitochondrial DNA polymorphisms are the most commonly used molecular tools for determination of kinship. Aim: To report a revision of 1,120 kinship cases (paternity and others) analyzed in our laboratory. Material and methods: Revision of all kinship cases analyzed between years 2001-2006. Autosomal and Y chromosome STRs and mitochondrial DNA polymorphisms were analyzed in DNA extracted from blood samples. Results: Paternity was excluded in 27.2 percent of cases. This figure did not change significantly along years. Most paternity exclusions were confirmed by the discordance in 5 genetic markers (30.5 percent), followed by exclusion of 4 and 6 genetic markers (20.3 and 20 percent respectively). Two studied cases were paternal and maternal exclusions, corresponding to a change of children between two families. In one case, the paternal line was assessed through Y chromosome markers, studying 16 STRs of this chromosome, positively confirming this paternal relationship. Another case was analyzed for maternal line using mitochondrial DNA analysis. In six cases, a genetic marker with a paternal-sibling mutation, was observed. The criteria for the determination of mutation was the finding of only one discordant marker between at ¡east thirteen markers analyzed in each case. Also, an increase or decrease in one unit repeated in tandem (tetranucleotide) between the alleged father and the son was also required. One subject had a double mutation. In this case, paternity was confirmed analyzing thirteen autosomic STRs and five Y-STRs. Conclusions: The authors have acquired great expertise in kinship analysis and had established criteria to solve complex kinship cases.

Estudio de tres loci hipervariables en población mixta chilena / Study of 3 hypervariable loci in a mixed chilean population

Background: Genetic markers are useful to study evolution parameters in populations and to determine kinship. Aim: To characterize three short tandem repeat loci in a sample of Chilean subjects and compare them with Caucasian and Hispanic populations. Material and methods: Three hundred ninety three unrelated subjects that were sent for genetic studies from courts of justice, were studied. The loci FESFPS, F13A01 and vWA in blood samples, were typified amplifying DNA by polymerase chain reactions. Results: The three studied loci were highly polymorphic. F13A01 and FESFPS were in Hardy-Weinberg genetic equilibrium. A significant excess of heterozygotes was detected for vWA locus. There were no differences in allele frequencies, according to ethnic origins of last names. Allele frequencies for F13A01 and vWA loci were similar to those of Hispanic populations of Unites States and FESFPS loci was different. Conclusions: All three loci had a high efficiency for genetic identification tests according to the estimated a priory exclusion probability

Análisis de paternidad utilizando cuatro marcadores de DNA amplificados mediante la reacción en cadena de polimerasa / Paternity analysis using 4 DNA markers amplified by polymerase chain reaction

Background: DNA typing in forensic analysis is a useful tool to analyze paternity due to its high discrimination power. Aim: To report the experience of Servicio Medico Legal in Santiago, resolving cases of dubious paternity. Subjects and methods: Four highly polymorphic loci, amplified by polymerase chain reactions, were analyzed in 153 cases of uncertain paternity. The paternity index was calculated for each case. Results: The four genetic markers analyzed provided an exclusion probability of 0.933 for the general population in Santiago. Thirty seven cases were excluded as parents. In 31 cases, the paternity index ranged from 19 to 100, considered as probable paternity and 77 cases had an index of over 100, considered as almost certain paternity. Eight cases had an index between 0.5 and 19, considered as inconclusive. All loci met Hardy-Weinberg expectations and their frequencies were similar to other data from people living in Santiago. Conclusions: The use of these genetic markers proved to be very useful, reliable and with a high exclusion power for paternity analysis

Análisis de paternidad en casos de incesto, utilizando polimorfismo del ADN de loci multialélicos / Paternity analysis in incest cases using DNA polymorphisms of multiallelic loci

The analysis of genetic markers in man allows to efficiently resolve cases of dubious paternity. Lately, the use of genetic markers derived from DNA analysis allows high exclusion probabilities. A particular case are those consultations whom the progenitors are closely related, in which the criteria to attribute paternity are modified. The present report explains the analysis methods and interpretation of results in situations of doubtful paternity in cases of incest between father and daughter, using monolocus DNA polymorphisms. The method is illustrated through the analysis of 4 cases seen at the Servicio Médico Legal of Santiago. To be able to determine paternity in these cases of incest, at least three multiallelic loci in which mother and son have different genotypes must be examined