Biostatistical basis of individualization and segregation analysis using the multilocus DNA probe MZ 1.3: results of a collaborative study

An informativity index for multilocus DNA fingerprints

An informativity index for multilocus DNA fingerprints, r, was developed. It is based upon the Shannon information that a paternal DNA fingerprint conveys about the offspring phenotype pattern. Both simulation and empirical data reveal that the index r is strongly correlated with the mean log likelihood ratio (paternity vs. nonpaternity) expected in trio cases of true paternity. Since r can be estimated from DNA fingerprints of unrelated individuals in advance, it will provide an easy means to assess the potential utility of a given probe/enzyme combination in kinship testing.

Calculation of paternity probabilities from multilocus DNA profiles

We describe a procedure for evaluation of paternity evidence from multi-locus DNA probe patterns. A computer program abstracts a "+/-" notation description from the multilocus profile and then calculates a paternity index based on observed phenotypic fragment frequencies. The biostatistical evaluation considers only bands found in the child and missing from the mother--a simplified approach that is at once robust and conservative. Mutations are of course taken into account. Particular features lending objectivity to the interpretation include computer reading and matching decisions, and specific recognition and statistical compensation for ambiguities ("faint orphans").

Multilocus DNA fingerprinting: the independence problem in quantitative paternity testing

A simulation study was performed in order to determine whether or not the assumption of independence, made in the quantitative analysis of multilocus DNA fingerprints, represents an inadmissible over-simplification. A total of 10,000 cases of true and false paternity, respectively, were simulated in twenty replicas of various genetic models. Log-likelihood ratios (paternity vs. non-paternity; LR) were calculated using published likelihood formulae and assuming position-wise independence. The resulting LR distributions were compared to (i) the results of a classical analysis of the underlying genotype data, and (ii) the distributions expected from the likelihood model employed in the LR calculations. Although considerable discrepancies were observed between these distributions, decision making about paternity appeared to be only marginally affected, especially when only a fraction of each multilocus DNA fingerprint was analyzed.

Paternity testing with oligonucleotide multilocus probe (CAC)5/(GTG)5: a multicenter study

The statistical analysis is reported of 256 paternity cases referred to seven different German laboratories for multilocus DNA fingerprinting with oligonucleotide probe (CAC)5/(GTG)5 and restriction enzyme HinfI. All parameters characteristic of multilocus DNA fingerprints were found to differ significantly between the contributing centres: the number of analyzed gel positions, the number of bands scored per individual, the probability of occurrence of a band at a particular position, and the band-sharing probabilities between the mother and both child and alleged father. Despite these differences, paternity cases could be divided clearly into two distinct subgroups on the basis of (i) offspring bands that could not be assigned to either the mother or the alleged father and (ii) the extent of band-sharing between child and alleged father. This partitioning, which is likely to correspond to true and false paternity, confirms previous findings for other multilocus probes. A goodness-of-fit test on the normalized number of bands scored per individual revealed no systematic deviations from commonly adopted analytical models regarding electrophoretic bands as independent entities. Log10-likelihood ratios of paternity vs. non-paternity were calculated utilizing one of these models, and a clear-cut partitioning was again obtained which coincides with that mentioned before. Only one case could not be decided unambiguously, and was either due to two independent mutations or to a close relative of the alleged father being the true father.