Portuguese population and paternity investigation studies with a multiplex PCR — the AmpFlSTR® Profiler Plus™
Introduction
Human identification is the ultimate goal for forensic genetics, either in criminal casework or in paternity testing. Short tandem repeat (STR) analysis is well established in forensic genetic laboratories.
DNA profiling is currently focused on the use of multiplex PCR which was developed including triplex, quadriplex and hexaplex systems [1], [2]. Multiplex systems are now commercially available [3] including more than six STR loci performed in one PCR reaction, giving matching probabilities in the range of more than 1 in a billion. One such system is the AmpFlSTR® Profiler Plus™ PCR Amplification Kit (PE Applied Biosystems) which co-amplifies the repeat regions of nine STR loci — D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820. A segment of the X–Y homologous gene amelogenin is also amplified.
In several European countries, DNA databases have been implemented with different multiplex systems [3], [4], [5]. These multiplex system loci form part of the 13 STR loci employed in the US National Databank CODIS (Combined DNA Index System). A Portuguese population sample was evaluated in order to obtain data concerning the application of AmpFlSTR Profiler Plus in paternity investigations and in population studies to implement a DNA database. These studies were performed according to the guidelines recommended by the DNA Commission of the International Society of Forensic Haemogenetics relating to the use of PCR-based polymorphisms [6].
Section snippets
Population sample
Samples from a total of 146 healthy unrelated Portuguese Caucasian individuals obtained from 83 paternity investigation cases requested by the Court were studied. All individuals and their parents were natives of Portugal, predominantly from the southern region.
Blood samples were collected and stored using UltraStain card (Fitzco) and DNA was extracted by the Chelex method.
Amplification and typing
DNA samples were amplified by multiplex PCR for D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317 and D7S820
Allele frequency estimates and forensic parameters
The observed allele frequency distributions in the Portuguese population sample for the nine loci analysed with the AmpFlSTR Profiler Plus are listed in Table 1. The genotype frequencies for these loci (data not shown) did not deviate from Hardy–Weinberg expectation based on the conventional chi-square method (P<0.01).
Statistical differences in allele frequencies were observed between this Portuguese Caucasian population and an Italian Caucasian population in D8S1179 (P<0.01), D21S11 (P<0.05)
Discussion
A Portuguese population sample was evaluated to obtain data concerning the application of AmpFlSTR Profiler Plus loci in paternity investigations and in population studies. Forensic statistical parameters such as power of discrimination, probability of exclusion and heterozygosity were according to those obtained by other authors [12]. The D5S818 locus presented the lowest forensic values, while D18S51 presented the highest forensic statistical parameters. The multiplex PCR investigated was
Acknowledgements
The authors thank Miss Isabel Lucas for excellent technical assistance.
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