Analysis of data and common mutations encountered during routine parentage testing in Zimbabwe

Abstract

We analyzed parentage data collected over a ten-year period in a Zimbabwean DNA testing laboratory. Parentage case types, prevalence, exclusion data, mutations rates and observed genotyping irregularities were analyzed. We report analysis results from 1303 cases. DNA extraction and STR typing was conducted using standard commercial kits. Paternity was the most requested test (87.37%) followed by the indirect biological kinship tests (7.01%). Duo paternity (motherless) was the most common paternity test for both regular and court cases. We observed 367 paternity exclusions from 1135 cases, giving an overall paternity exclusion rate of 32.33%. Maternity had the lowest exclusion rate (8.33%), with criminal cases having the highest paternity (61.11%) and maternity (33.33%) exclusion rates. The number of mismatched STR loci ranged from 2–12 for duo cases and 4–18 for the trio cases. FGA, D2S1338, D18S51 and D2S441 were the most informative markers for exclusion. We detected 30 mutations out of 837 cases with an estimated paternal and maternal mutation rate of 0.0021 and 0.0011 respectively. Triallelic patterns were only observed at the TPOX locus with allele 10 and 11 being the extra alleles transmitted. Our report provides forensic parameters which can improve parentage and forensic analysis in Zimbabwe.