Lucía Cifuentes

Probability of Exclusion in Paternity Testing: Time to Reassess*

ABSTRACT: The average exclusion probability is a measure of efficiency in paternity testing; it refers to the a priori ability of a battery of tests to detect paternity inconsistencies. This parameter measures the capacity of the system to detect a false accusation of paternity. Traditionally, this average exclusion probability has been estimated as the probability of excluding a man who is not the father by an inconsistency in at least one of the studied loci. We suggest that this criterion should be corrected, as currently the presumed father is excluded when at least three genetic inconsistencies are found with the child being tested, not just one. This change of criterion has occurred because of the use of microsatellite loci, whose mutation rates are much greater than those of the coding genes used previously in paternity studies. We propose the use of the average probability of exclusion for at least three loci (not only one), as an honest measure of the combined probability of exclusion of several loci, and we propose an algebraic expression to calculate it.

Quantitative analysis of genetic differentiation among European and Chilean strains of Drosophila subobscura.

An analysis of the interpopulational differences observed between four European and four Chilean stocks of Drosophila subobscura, with regard to wing size, egg-to-adult development time and preadult viability, shows highly significant differences between the eight stocks irrespective of the continent from which the flies are derived. The divergence of the local populations with regard to the quantitative traits described here, supplements other evidence of interpopulational differences in mating activity, chromosomal and enzyme polymorphisms. These together indicate that the evolutionary process that promotes race formation is relatively rapid, bearing in mind that D. subobscura was detected for the first time in South America in 1978.

DNA extraction from formalin-fixed laryngeal biopsies: Comparison of techniques

Abstract Conclusion: PCR-quality DNA could be extracted from formalin-fixed paraffin-embedded (FFPE) samples with amplicons of at least 390 bp. Paraffin removal was not a necessary step. Proteinase K digestion was as efficient as the commercial kit for DNA extraction with a lower cost. Objectives: To compare different DNA extraction protocols for FFPE samples and to describe the suitability of the extracted DNA for PCR reactions. Methods: For deparaffinization the following techniques were compared: alkaline heat, xylene, and no removal. For DNA extraction, proteinase K digestion and organic extraction were compared. A commercial extraction kit was included as standard. DNA quality was assessed by PCR amplification of the HFE gene, for amplicons of 208 and 390 bp. Results: Extraction with the commercial kit and proteinase K digestion were more efficient than other techniques, with no statistical difference between them for both amplicons. The proteinase K digestion buffer had a cost of U

Prevalence of the 35delG mutation in the GJB2 gene in two samples of non-syndromic deaf subjects from Chile

0.2 per sample and the commercial kit of U

Allele frequencies for six STR in a Chilean population.

7 per sample.

CTG repeats at the myotonic protein kinase gene in a healthy Chilean population sample

Hearing loss is the most common inherited sensorial deficiency in humans; about 1 in 1000 children suffer from severe or profound hearing loss at birth. Mutations in the GJB2 gene are the most common cause of prelingual, non-syndromic autosomal recessive deafness in many populations; the c.35delG mutation is the most common in Caucasian populations. The frequency of the c.35delG mutation was estimated in two samples of deaf patients from Santiago, Chile. Unrelated non-syndromic sensorioneural deaf patients were examined: Group 1 consisted of 47 unrelated individuals with neurosensory deafness referred to the Chilean Cochlear Implant Program; Group 2 included 66 school children with prelingual deafness attending special education institutions for deaf people. Individuals with profound to moderate isolated neurosensory hearing loss with unknown etiology were included. The presence of the c.35delG mutation was evaluated by the allele-specific polymerase chain reaction method (PCR), and in some cases it was confirmed by direct DNA sequencing of the coding region of the GJB2 gene. Deaf relatives were present in 20.3% of the cases. We found 19.5% (22/113) patients with the c.35delG mutation, 6 of them homozygous; these rates are similar to frequencies found in other Latin American countries.

Gene Frequencies for Three Hypervariable DNA Loci in a Chilean Population of Mixed Ancestry

A sample of Chilean individuals from the northern area of Santiago, the capital of Chile, was studied. The current Chilean population was sprung from the admixture between aborigine populations of mongoloid origin (Amerindians) and Spanish conquerors of Caucasian origin. Blood samples from unrelated blood donors were randomly collected in the Hospital San Jose. An appropriate informed consent was obtained from all of them according to the Ethical Board of the Medicine School of the University of Chile.

Segregation Distortions of the ABO and Rh Systems in Malformed Newborns

Objectives –  To study the variability at the myotonic dystrophy protein kinase (DMPK) gene in a Chilean sample of healthy people. DM1 is an autosomal dominant disorder caused by an expansion of a (CTG) repeat at the 3′‐UTR of the gene DMPK. Healthy individuals have alleles under 35 repeats and diseased individuals have over 50.

Muir-Torre Syndrome: case report and molecular characterization

Blood samples were collected in tubes containing ACD from 121 unrelated individuals who asked paternity analysis in The Clinical Hospital of the University of Chile during the years 2000 and 2001. The method presented by Comey (1) was used to remove DNA from the samples. The three STR were amplified using 1 ng of DNA for each PCR reaction, and the fragments electrophoresed through 6% acrylamide gels and silver stained, according to the manufacturers recommendations (2).

Paternity analysis when the putative father is missing: first case in Chile.

This study compares the segregation of the ABO and Rh systems between malformed newborns and a control group with two purposes: (1) to evaluate the participation of genetic factors associated with these blood groups in the production of congenital malformations, and (2) to prove, indirectly, the existence of reproductive losses associated with congenital malformations. The newborns and their mothers were typed for ABO and Rh groups. Gene frequencies were similar in malformed and control newborns. In the female malformed newborns, an excess of O-B pairs and a deficit of B-B pairs in the ABO system, and an excess of Rh(-)-Rh- pairs in the Rh system were found.