Browsing by Author "Geada, Helena"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Analysis of NGM STR loci in South Portuguese PopulationPublication . Ribeiro, Teresa; Dario, Paulo; Vital, Nádia; Sanches, Susana; Espinheira, Rosa; Geada, Helena; Costa Santos, JorgeAllele frequencies and other relevant forensic parameters of 15 loci studied with Applied Biosystems AmpFlSTRs NGM Kit were calculated in a population of individuals residing in the South of Portugal. Blood stain samples were obtained from a total of 350 unrelated individuals involved in paternity testing casework. This new kit has five loci not present in any other kit used in our laboratory (Promega Powerplex 16 System and Applied Biosystems Identifiler Plus): D10S1248, D22S1045, D2S441, D1S1656 and D12S391. The NGM multiplex kit is used in our forensic casework as an auxiliary screening tool to solve deficient casework such as fatherless paternity testing, and to help in paternity investigations with one genetic incompatibility after the routine seventeen loci typing. Furthermore, this five loci included in the European Standard Set are also recommended by the European Network of Forensic Science Institutes (ENFSI) and the European DNA Profiling group (EDNAP). These studies are necessary to calculate statistical forensic parameters such as power of discrimination, power of exclusion or minimum allele frequencies. Statistical parameters such as heterozigoty, homozigoty or allele frequencies were determined with Arlequim V3.5 and results compared with the ones reported in previous similar studies. As final remark, is important to remember that this kind of study is highly important for the Forensic Laboratories accreditation achievement
- Diversidade Genética na População de Macau em 15 Loci STRsPublication . Cruz, Carla; Viriato, Luís; Vieira, Claudia; Ribeiro, Teresa; Espinheira, Rosa; Geada, HelenaDecorridos 450 anos de permanência de população portuguesa em território macaense, no dia 20 de Dezembro de 1999, teve lugar a transferência definitiva da soberania de Macau para a República Popular da China. Tendo como objectivo a caracterização genética de uma população originária e residente em Macau e posterior comparação com a população portuguesa, foi efectuado um estudo de um conjunto de 15 loci STRs, dos quais 13 constituem o sistema CODIS e 2 são pentanucleótidos (Penta E e Penta D)A população de Macau mostrou desvios do equilibrio de Hardy-Weinberg nos sistemas D3S1358, TH01, D8S1179, D16S539 e PENTA D, apresentando neste último o desvio mais significativo. Verifica-se que o locus PENTA E é o mais polimórfico e discriminante na população em estudo. A comparação da população macaense com a população portuguesa revelou alelos exclusivos da primeira nos sistemas D18S51 (alelo 24), PENTA E (alelo 24), D5S818 (alelo 7), D7S820 (alelo 9.1), CSF1PO (alelos 14 e 15), vWA (alelo13) e FGA (alelos 13, 16, 25.2 e 26.2). No sistema TPOX a distribuição das frequências alélicas é muito próxima da população portuguesa. Em relação a todos os outros loci, foram detectadas diferenças significativas das frequências dos alelos entre as duas populações. Comparando a população macaense com populações chinesas2,3, verifica-se que estas apresentam semelhanças quanto à distribuição dos alelos nos sistemas estudados, o que sugere proximidade entre as referidas populações.
- Identificação genética a partir de lâminasPublication . Ribeiro, Teresa; Vieira da Silva, Cláudia; Lucas, Isabel; Dario, Paulo; Geada, Helena; Espinheira, Rosa
- Identification by mtDNA of exchanged human body remainsPublication . Cruz, Carla; Ribeiro, Teresa; Vieira - Silva, Cláudia; Lucas, Isabel; Geada, Helena; Espinheira, RosaMtDNA offers some advantages over genomic DNA markers for the identification of human remains. Its sequence is completely determined and the high copy number increases the chance to obtain mtDNA in cases of limited quantity or degraded autosomal DNA. The maternal mode of inheritance without recombination during the meiosis process allows maternal lineage identification by a simple direct comparison of the mtDNA sequence of mother and child or between brothers and sisters. CASE HISTORY: Five Portuguese citizens were killed in African. Three of them were identified and removed to Portugal, where they were buried. Two children were reported as missing. One year later, two skeletons were found in a grave 500 metres from the crime scene. Genetic typing of DNA extracted from skeletal remains was performed in order to establish their identities. One of the mothers of the two missing minors was excluded from the maternity of the skeletal remains. The hypothesis was raised of an identity exchange of the three corpses previously removed to Portugal. These were then exhumed and subjected to genetic analysis to achieve biological identification. Although teeth and bones are reliable sources of DNA, it was difficult to obtain results namely from those retrieved in Africa. As we expected, these required more modifications to standard protocol. The state of the bones samples from this continent was poor, probably due to the humidity, temperature and other African environmental conditions and soil characteristics that accelerate the degradation process. Low amounts, high fragmentation, and contamination of the DNA are the main problems associated with this kind of sample. In some cases, increasing the amount of DNA helped to overcome the first problem, but in some others lead to negative results, which can be explained by an increase of Taq polymerase inhibitors in the mix reaction. Regarding the degraded DNA, the application of different primers to the HVI and HVII regions allowed the amplification of two shorter overlapping fragments for each region and the reconstruction of HVI and HVII sequences. Several dilutions of DNA extract were tested to decrease the hypothetical contaminants that would act as Taq polymerase inhibitors. The coincidence of each of the five body sequences with one of the alleged mothers suggests a maternal relationship. A fraternal relationship was detected between bodies 2 and 5. These share the same mtDNA sequence with mother 3. The results supported the hypothesis of exchanged human body remains. Autosomal STR loci analysis was performed and confirmed the identity of the human remains. MtDNA analysis was a useful tool to solve this case. Although it cannot be used to definitely identify the corpses, it provided evidence of a maternal relationship and, consequently, the exchange of human body remains.
- Portuguese Population Study with 16 Y-STR LociPublication . Geada, Helena; Baptista, Joana; Felgueiras, Miguel; Vieira Da Silva, Cláudia; Cruz, Carla; Lucas, Isabel; Ribeiro, Teresa; Espinheira, RosaAlthough autosomal STRs are commonly used for forensic investigations, Y-chromosome STRs provide very useful information in paternity investigation cases without alleged father and investigation cases where paternal lineage identification can be assessed. The aim of this study is to present an extended 16 Y-STR Portuguese Population Database of 214 Southern Portugal individual samples for forensic purpose, including the 8 Y-STR minimal haplotype – DYS19, DYS389 I/II, DYS390, DYS391, DYS392, DYS393, DYS385 (Gusmão et al, 2001, D Syndercomb-Court, personal communication) and Y-STR loci included in the Y-Chromosome GEP-ISFG collaborative exercise – DYS437, DYS438, DYS439, DYS460, DYS461, GATA A10, GATA C4, GATA H4.When performing a 16 Y-STR study the genetic diversity was successfully increased. With the 8 Y-STR minimal haplotype, haplotype clusters can be detected involving several non-related individuals, whereas, with a 16 Y-STR haplotype, haplotype clusters involve only 2 or 3 non-related individuals. The 16 Y-chromosome STR haplotype seem to be extremely important to solve complex forensic cases and in population, studies to obtain unique paternal profiles and to determine specific population characteristics
- Superfecundação heteropaterna na investigação de paternidadePublication . Ribeiro, Teresa; Vieira Da Silva, Cláudia; Dario, Paulo; Geada, Helena; Espinheira, Rosa
- vWA STR Locus - Structure and variabilityPublication . Cruz, Carla; Vieira da Silva, Cláudia; Lucas, Isabel; Ribeiro, Teresa; Espinheira, Rosa; Geada, HelenaThe biological individualization of samples is studied through DNA STR loci analysis and is the principal goal of Forensic Genetics. STR loci study was initiated in the 90s on the majority of Forensic Laboratories. vWA is one of the most studied STR loci all over the world. It is included in any STR set proposed by Forensic Groups as the 13 core loci of the CODIS System used in routine cases by most Forensic Genetic Laboratories. When performing paternity investigation and identification cases with STR loci, once in a while we came through rare or new alleles. Sequencing is essential to confirm the structure of these alleles. Also in mutation cases, especially in primer binding mutation cases, allele sequence should be performed. The high primer binding mutation observed in this locus and the interest in structure analysis of rare alleles observed in certain population groups were the main reasons for performing vWA sequence. More than one hundred vWA samples have been sequenced with DNA Sequencing Kit Big Dye Terminator Cycle Sequencing with forward and reverse primers (Kimpton et al, 1992 GenBank M25858). Sequencing was performed in an ABIPRISM 377 DNA Sequencer and analyzed by Sequencing Analysis. In this study we will present the structural analysis of vWA alleles from allele 11 to allele 22 studied in two main populations – a Portuguese population and an African population mainly from Cabo Verde Islands and Angola