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Abstract
In forensic genetics the determination of an individual's genetic profile is mainly used in particular cases where human individual identification is required and in kinship-based investigations. The probability of identity is calculated using the allelic frequencies of each marker of a given genetic profile. To determine this genetic profile, molecular markers, most often microsatellite type, called STRS (Short Tandem Repeats) are used, which are dispersed throughout the human genome. The choice of this type of markers comes from a number of factors, namely because they have a high discrimination power and are easily amplified through PCR reaction. In this case, were used STRs present on the X chromosome because it exhibits a distinct mode of transmission. In male individuals, only one copy is transmitted entirely to female offspring, allowing for direct reconstruction of the haplotype; whereas in female individuals the information provided by X chromosome recombination is an additional insight into the history of human populations, altering genetic variation in each generation.
In this study, 10 X-STRs were genetically characterized (DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS7423, DXS6809, DXS7132, DXS9902 and DXS6789) and their efficiency in forensic applications in the population of Nigeria, a country located in West Africa in the Gulf of Guinea. The sample consisted of 230 unrelated male individuals from three of Nigeria's largest ethnic groups, namely Hausa (n= 90), Yoruba (n=44) and Igbo (n= 96).
The analysis of significant association between loci pairs, based on the exact linkage disequilibrium (LD) test. did not provide evidence of statistically significant LD (p>0.0011) between the markers studied in the present sample.
Genetic affinities among the three ethnic groups studied was analyzed by genetic. distances (Fs7) and molecular variance analysis (AMOVA). Based on the results, no significant differences were detected, which supports the homogeneity between the three groups of Nigeria studied for the X-STRs used.
Allelic frequencies were also compared between the populations of Nigeria, Angola, Mozambique, Algeria, Ivory Coast, Egypt, Ghana, Guinea-Bissau, Morocco, Tunisia and Uganda. No significant genetic differences of Fst were detected between the three groups in Nigeria and the sub-Saharan populations of Angola, Mozambique, Ivory Coast,Ghana, Guinea-Bissau and Uganda. Therefore, the significant differences found resulted from the comparison with the North African groups, namely Algeria, Egypt, Morocco and Tunisia.
In the characterization of the population of Nigeria, it was observed that the DXS6809 locus showed the highest degree of polymorphism (0.852), being also the locus with the In forensic genetics the determination of an individual's genetic profile is mainly used in particular cases where human individual identification is required and in kinship-based investigations. The probability of identity is calculated using the allelic frequencies of each marker of a given genetic profile. To determine this genetic profile, molecular markers, most often microsatellite type, called STRS (Short Tandem Repeats) are used, which are dispersed throughout the human genome. The choice of this type of markers comes from a number of factors, namely because they have a high discrimination power and are easily amplified through PCR reaction. In this case, were used STRs present on the X chromosome because it exhibits a distinct mode of transmission. In male individuals, only one copy is transmitted entirely to female offspring, allowing for direct reconstruction of the haplotype; whereas in female individuals the information provided by X chromosome recombination is an additional insight into the history of human populations, altering genetic variation in each generation.In this study, 10 X-STRs were genetically characterized (DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS7423, DXS6809, DXS7132, DXS9902 and DXS6789) and their efficiency in forensic applications in the population of Nigeria, a country located in West Africa in the Gulf of Guinea. The sample consisted of 230 unrelated male individuals from three of Nigeria's largest ethnic groups, namely Hausa (n= 90), Yoruba (n=44) and Igbo (n= 96).The analysis of significant association between loci pairs, based on the exact linkage disequilibrium (LD) test. did not provide evidence of statistically significant LD (p>0.0011) between the markers studied in the present sample.Genetic affinities among the three ethnic groups studied was analyzed by genetic. distances (Fs7) and molecular variance analysis (AMOVA). Based on the results, no significant differences were detected, which supports the homogeneity between the three groups of Nigeria studied for the X-STRs used.Allelic frequencies were also compared between the populations of Nigeria, Angola, Mozambique, Algeria, Ivory Coast, Egypt, Ghana, Guinea-Bissau, Morocco, Tunisia and Uganda. No significant genetic differences of Fst were detected between the three groups in Nigeria and the sub-Saharan populations of Angola, Mozambique, Ivory Coast,Ghana, Guinea-Bissau and Uganda. Therefore, the significant differences found resulted from the comparison with the North African groups, namely Algeria, Egypt, Morocco and Tunisia.In the characterization of the population of Nigeria, it was observed that the DXS6809 locus showed the highest degree of polymorphism (0.852), being also the locus with theIn forensic genetics the determination of an individual's genetic profile is mainly used in particular cases where human individual identification is required and in kinship-based investigations. The probability of identity is calculated using the allelic frequencies of each marker of a given genetic profile. To determine this genetic profile, molecular markers, most often microsatellite type, called STRS (Short Tandem Repeats) are used, which are dispersed throughout the human genome. The choice of this type of markers comes from a number of factors, namely because they have a high discrimination power and are easily amplified through PCR reaction. In this case, were used STRs present on the X chromosome because it exhibits a distinct mode of transmission. In male individuals, only one copy is transmitted entirely to female offspring, allowing for direct reconstruction of the haplotype; whereas in female individuals the information provided by X chromosome recombination is an additional insight into the history of human populations, altering genetic variation in each generation.In this study, 10 X-STRs were genetically characterized (DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS7423, DXS6809, DXS7132, DXS9902 and DXS6789) and their efficiency in forensic applications in the population of Nigeria, a country located in West Africa in the Gulf of Guinea. The sample consisted of 230 unrelated male individuals from three of Nigeria's largest ethnic groups, namely Hausa (n= 90), Yoruba (n=44) and Igbo (n= 96).The analysis of significant association between loci pairs, based on the exact linkage disequilibrium (LD) test. did not provide evidence of statistically significant LD (p>0.0011) between the markers studied in the present sample.Genetic affinities among the three ethnic groups studied was analyzed by genetic. distances (Fs7) and molecular variance analysis (AMOVA). Based on the results, no significant differences were detected, which supports the homogeneity between the three groups of Nigeria studied for the X-STRs used.Allelic frequencies were also compared between the populations of Nigeria, Angola, Mozambique, Algeria, Ivory Coast, Egypt, Ghana, Guinea-Bissau, Morocco, Tunisia and Uganda. No significant genetic differences of Fst were detected between the three groups in Nigeria and the sub-Saharan populations of Angola, Mozambique, Ivory Coast,Ghana, Guinea-Bissau and Uganda. Therefore, the significant differences found resulted from the comparison with the North African groups, namely Algeria, Egypt, Morocco and Tunisia.In the characterization of the population of Nigeria, it was observed that the DXS6809 locus showed the highest degree of polymorphism (0.852), being also the locus with the highest discrimination power (0.979) in female and the highest exclusion power (0.881) in trios involving daughters. On the other hand, the least polymorphic locus was the DXS7133 with a genetic diversity value of 0.564, which also had the lowest discriminating power in female (0.561) and the lowest probability of exclusion in trios involving daughters (0.375). The high values of accumulated discrimination power prove the potential of the decaplex system developed in identification studies, and the high probability of exclusion obtained confirm the usefulness of these markers in kinship tests, particularly in paternity tests involving daughters when complete trios are analyzed or in father/daughter duos.
