DNA mixtures are frequently encountered in forensic casework especially in cases of sexual assault. When evidence is recovered, the sample may have come from multiple contributors in different proportions. The first part of this study examines the fidelity of contributor proportions by using the residual to analyze known mixture samples. The coefficient of determination between the expected and observed proportions was also determined and used to assess the fidelity of mixture proportions. The second part of this study involved separating major and minor contributors in a mixture by characterizing the observed proportions. Results for the 2-person mixture show that as the mass of amplified DNA decreases, the number of allele dropouts increases. Furthermore, as mass decreases, the level of variation between the expected and observed proportions increases, as determined by the residuals and the coefficients of determination. In addition, as mixture proportions become more disparate the amount of variations between the expected and observed proportions are not as great as the mass. For the 3-person mixtures, as mass decreases, the residuals increase. Also, when the coefficient of determination of the 3-person mixtures were compared to those obtained with the 2-person mixtures, it was determined that the R2 were larger for the former. This was a result of higher total amplification masses. In mixture 1:2/2:1, major and minor proportions are not distinguishable In mixture 1:4/4:1, major and minor proportions can be distinguished at 1 ng. In mixture 1:9/9:1, proportions are distinguishable at 1, and 0.5 ng. Mixtures could not be distinguished at the 0.25 ng level, despite proportion and is the result of the increase in variation with decreasing mass.

Made available in DSpace on 2015-04-01T14:16:04Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1809210 bytes, checksum: e118d10e8ea156df56a7871608a59d7b (MD5) Previous issue date: 2014-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Human identification is based on analyzing DNA through present throughout the genome molecular markers. These markers are transmitted from parents to offspring by heredity. STR markers are currently the most commonly used genetic markers in Forensic Genetics due to their high polymorphism, high reproducibility, possibility of being amplified by PCR in multiple copies in a single reaction, and minute quantities of DNA (1ng). The DNA test that allows individualization of the people is essential tool to the solution of forensic human identification cases, sex crimes, crime scenes (including or excluding suspects), mass disasters, and its result is presented in statistical calculations that consider allele frequency of markers used. So it is important to know the allele frequencies presented in the regional population so that the results are the most reliable possible. In this study , 15 autossomal markers (loci) STR or microsatellite (CSF1PO, D13S317, D16S539, D18S51, D19S433, D21S11, D2S1338, D3S1358, D5S818, D7S820, D8S1179, FGA, TH01, and VWA TPOX) were studied in 766 unrelated individuals paraibanos, demonstrating a tri population - hybrid formed Africans (25.86 %), Amerindian (6.81 %) and Europeans (67.33 %). The most informative were D21S11 and FGA, and were less informative TPOX, D7S820 and D13S317. The results are important for a database with allele frequencies found in Paraiba population can serve as a useful basis for calculating forensic practice in the State of Paraíba. / A identificação humana está baseada na análise do DNA através de marcadores moleculares presente em todo o genoma. Estes marcadores são transmitidos de pais para filhos por hereditariedade. Atualmente os marcadores STR são os marcadores genéticos mais utilizados em Genética Forense devido ao seu elevado polimorfismo, alta reprodutibilidade, possibilidade de serem amplificados por PCR em inúmeras cópias numa só reação e em mínimas quantidades de DNA (1ng). O exame de DNA que permite a individualização das pessoas é ferramenta indispensável à solução de casos forenses de identificação humana, crimes sexuais, locais de crime (incluindo ou excluindo suspeitos), desastres em massa, e tem seu resultado apresentado em cálculos estatísticos que consideram a frequência alélica dos marcadores usados. Por isso é importante o conhecimento das frequências alélicas apresentadas na população regional de forma que os resultados sejam os mais fidedignos possíveis. Neste trabalho, 15 marcadores autossômicos (loci) STR ou microssatélites (CSF1PO, D13S317, D16S539, D18S51, D19S433, D21S11, D2S1338, D3S1358, D5S818, D7S820, D8S1179, FGA, TH01, TPOX e vWA) foram estudados em 766 indivíduos paraibanos não aparentados, demonstrando uma população tri - hibrida, formada de africanos (25,86%), ameríndios (6,81%) e europeus (67,33%). Os mais informativos foram D21S11 e FGA, e os menos informativos foram TPOX, D7S820 e D13S317. Os resultados são importantes para que um banco de dados com as frequências alélicas encontradas na população paraibana possa servir de base de cálculo útil para prática forense no Estado da Paraíba.