PubMed Health⌕ Search

Biomedical subjects

Paula Sánchez-Diz

Publications and source records attributed to Paula Sánchez-Diz.

9 recordsLinked to original sources
PubMed2005

Forensic DNA-typing technologies: a review.

Since the discovery of deoxyribonucleic acid (DNA) profiling in 1985, forensic genetics has experienced a continuous technical revolution, both in the type of DNA markers used and in the methodologies or its detection. Highly informative and robust DNA-typing systems have been developed that have proven to be very effective in the individualization of biological material of human origin. DNA analysis has become the standard method in forensic genetics used by laboratories for the majority of forensic genetic expertise and especially in criminal forensic casework (stain analysis and hairs) and identification.

DNA↗
PubMed2003

Results of the GEP-ISFG collaborative study on the Y chromosome STRs GATA A10, GATA C4, GATA H4, DYS437, DYS438, DYS439, DYS460 and DYS461: population data.

The Spanish and Portuguese ISFG Working Group (GEP-ISFG) carried out a collaborative exercise in order to asses the performance of two Y chromosome STR tetraplexes, which include the loci DYS461, GATA C4, DYS437 and DYS438 (GEPY I), and DYS460, GATA A10, GATA H4 and DYS439 (GEPY II). The groups that reported correct results in all the systems were also asked to analyse a population sample in order to evaluate the informative content of these STRs in different populations. A total of 1020 males out of 13 population samples from Argentina, Brazil, Costa Rica, Macao, Mozambique, Portugal and Spain were analysed for all the loci included in the present study. Haplotype and allele frequencies of these eight Y-STRs were estimated in all samples. The lowest haplotype diversity was found in the Lara (Argentina) population (95.44%) and the highest (99.90%) in Macao (China). Pairwise haplotype analysis showed the relative homogeneity of the Iberian origin samples, in accordance with what was previously found in the European populations for other Y-STR haplotypes (http://www.ystr.org). As expected, the four non-Caucasian samples, Macao (Chinese), Mozambique (Africans), Costa Rica (Africans) and Argentina (Lara, Amerindians), show highly significant Phist values in the pairwise comparisons with all the Caucasian samples.

Chromosomes, Human, Y↗
PubMed2003

Results of the GEP-ISFG collaborative study on two Y-STRs tetraplexes: GEPY I (DYS461, GATA C4, DYS437 and DYS438) and GEPY II (DYS460, GATA A10, GATA H4 and DYS439).

A collaborative exercise was carried out by the Spanish and Portuguese ISFG Working Group (GEP-ISFG) in order to evaluate the performance of two Y-chromosome STR PCR tetraplexes, which include the loci DYS461, GATA C4, DYS437 and DYS438 (GEPY I), and DYS460, GATA A10, GATA H4 and DYS439 (GEPY II). The participating laboratories were asked to type three samples for the eight markers, using a specific amplification protocol. In addition, two control samples, with known haplotypes, were provided. The results obtained by the 13 different participating laboratories were identical, except for two laboratories that failed to type correctly the same two samples for GATA C4. By sequence analyses, two different GATA C4 allele structures were found. One control sample (allele 21) and two questioned samples (allele 22, correctly typed by all the laboratories, and allele 25) presented the following repeat structure: (TCTA)4(TGTA)2(TCTA)2(TGTA)2(TCTA)n, but different from the one found for allele 26 in one sample included in this exercise, as well as in the second control sample (allele 23), namely (TCTA)4(TGTA)2(TCTA)2(TGTA)2(TCTA)2(TGTA)2(TCTA)n. The collaborative exercise results proved that both Y-tetraplexes produce good amplification results, with the advantage of being efficiently typed using different separation and detection methodologies. However, since GATA C4 repeat presents a complex structure, with alleles differing in sequence structure, efficient denaturing conditions should be followed in order to avoid typing errors due to sizing problems.

Alleles↗
PubMed2003

Bimodal allele frequency distribution at Y-STR loci DYS392 and DYS438: no evidence for a deviation from the stepwise mutation model.

A deviation from the stepwise mutation model (SMM) has been suggested for the trinucleotide Y-STR locus DYS392, based upon its bimodal allele frequency distribution in various populations. The same type of distribution is also observed for the pentanucleotide Y-STR DYS438. In order to verify whether a departure from an SMM is likely for these two loci, we studied a large number of Portuguese male DNA samples typed for the two loci and in addition, for the Y-STR loci DYS19, DYS389I/II, DYS390, DYS391 and DYS393. The compatibility of the observed allele frequency spectrum with an SMM was assessed by an apportionment of the molecular variance among, and consideration of the molecular distances between, haplotype groups defined according to their allelic state at each of the two markers of interest. For haplotypes carrying either modal alleles 11 or 13 of DYS392, 18.6% of the molecular variance of the remaining Y-STR background could be attributed to variation between the two groups. When all pairwise Phi(st) values between haplotype groups were compared, group 12 was found to be closer to 11 than to 13, and group 14 was much closer to 13 than to 12 and 11. It may therefore be concluded that DYS392 allele 13 represents an evolutionary lineage with little or no relationship to 11 and 12. Furthermore, allele 14 is a one-step neighbour of 13 and is therefore likely to represent an offshoot from group 13. For haplotypes carrying either modal allele 10 or modal allele 12 of DYS438, 27.7% of the molecular variance of the Y-STR background was found to be due to variation between the two groups. Comparison of the other pairwise Phi(st) values indicated that group 10 was closer to 9 and 11 than to 12, and that group 12 was closer to 11 and 13 than to 10. The lineages defined by the two modal alleles of DYS438 therefore also seem to be phylogenetically distant. When the two loci were analysed in combination, using the standardised linkage disequilibrium measure (D'), a strong association was noted between alleles DYS392*11 and DYS438*10 (D'=0.70) and between DYS392*13 and DYS438*12 (D'=0.72). Taken together, these results show that the bimodal allele frequency distributions of DYS392 and DYS438 are explicable in terms of (probably the same) historical and demographic causes, rather than a mutational mechanism other than SMM. The loci do therefore not appear to warrant any special attention when applied in population genetic or forensic studies.

Chromosomes, Human, Y↗
PubMed2003

Grouping of Y-STR haplotypes discloses European geographic clines.

Y-STR haplotypes are widely studied in Europe and an extensive databasing effort has been conducted (http://www.ystr.org). The distribution of these haplotypes has been considered to present no evidence for substructure at central and southern European level. This picture contrasts with the one that results from Y haplogroups defined by binary markers. This paradox has been solved by admitting that the high STR mutation rate and corresponding recurrence has erased geographic structuration. This explanation prompted us to reanalyse Y-STR haplotypes distribution bearing in mind the commonly admitted model for the generation of diversity in these markers, namely the stepwise mutation model (SMM) and, thus, taking the molecular distance between haplotypes into consideration. Accordingly, we have studied the European distribution of the two most frequent haplotypes in the Iberian Peninsula and their one step neighbours using the European samples deposited in the Y STR database (http://www.ystr.org). For the first group we found a clear-cut decreasing W-E gradient, while for the second the highest frequencies were found in the Iberian Peninsula (3.98% in Portugal and 3.85% in Spain), dropping to 2.88% in France and showing a less well defined SW-NW gradient. Furthermore, we have tested the agreement between haplotype groups and binary markers haplogroups in a random sample of 292 individuals from Northern Portugal. Our results demonstrate that (a) Y-STR haplotype data can be used for wide-scale anthropological approaches disclosing information that has been considered only available through binary markers and (b) forensic use of continental databases needs careful refinement, due to the macro-geographic pattern now evidenced.

Chromosomes, Human, Y↗
PubMed2002

Point mutations in the flanking regions of the Y-chromosome specific STRs DYS391, DYS437 and DYS438.

Sequence analysis of the DNA fragments amplified with the DYS391, DYS437 and DYS438 primers allowed the detection of biallelic polymorphisms in the flanking region of these STR loci. In this work, we describe a methodology where both the STR alleles and the SNPs at these loci are typed. Sequencing of chimpanzee (Pan troglodytes) homologous loci was performed and the ancestral state of the SNPs was determined. The allele distribution of these biallelic markers was analysed within different haplogroups. For DYS391, allele 1 was found in all samples from haplogroups E3a and E* (xE3a). DYS437 allele 1 was present in all haplogroup E3a samples and absent in the haplogroup E* (xE3a). The presence of allele 1 of DYS438 was restricted to haplogroup J. The SNP typing can be helpful in distinguishing STR haplotype identity by descent from identity by state, thus proving to be very informative in forensic investigations.

Animals↗
PubMed2002

The making of the African mtDNA landscape.

Africa presents the most complex genetic picture of any continent, with a time depth for mitochondrial DNA (mtDNA) lineages >100,000 years. The most recent widespread demographic shift within the continent was most probably the Bantu dispersals, which archaeological and linguistic evidence suggest originated in West Africa 3,000-4,000 years ago, spreading both east and south. Here, we have carried out a thorough phylogeographic analysis of mtDNA variation in a total of 2,847 samples from throughout the continent, including 307 new sequences from southeast African Bantu speakers. The results suggest that the southeast Bantu speakers have a composite origin on the maternal line of descent, with approximately 44% of lineages deriving from West Africa, approximately 21% from either West or Central Africa, approximately 30% from East Africa, and approximately 5% from southern African Khoisan-speaking groups. The ages of the major founder types of both West and East African origin are consistent with the likely timing of Bantu dispersals, with those from the west somewhat predating those from the east. Despite this composite picture, the southeastern African Bantu groups are indistinguishable from each other with respect to their mtDNA, suggesting that they either had a common origin at the point of entry into southeastern Africa or have undergone very extensive gene flow since.

Africa↗
PubMed2002

STR data for the AmpFlSTR Profiler Plus loci from Greece.

Allele frequencies for the nine STRs included in the AmpFlSTR Profiler Plus kit (D3S1358, VWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820) were estimated from a sample of 143 unrelated individuals living in different regions of Greece.

Gene Frequency↗