Mendelian errors can be detected in parent-offspring pairs or trios. In principle, this method of error detection is less efficient than evaluating concordance of duplicate samples because some genotyping errors are consistent with Mendelian inheritance (e.g. offspring of AB and BB parents, with a true BB genotype called as AB). However, Mendelian errors can be used to detect clustering problems that are not detectable with duplicate concordance. For example, consider a SNP assay in which the AA and AB clusters merge together and are both called as AA, while the actual BB cluster is called as AB. In this case, two AB parents (both called as AA) with a BB offspring (called as AB) would generate a Mendelian error. Similarly, Mendelian errors can detect SNPs with null alleles (N) segregating. For example, one parent as AN, the other as BB and the offspring as BN would give apparently inconsistent genotypes of AA, BB and BB, respectively. In both cases, a duplicate sample would give concordant results
