The effect of differences in gene frequency on probability of paternity

Knowledge of gene frequencies in populations is required for the calculation of probability of paternity. The question remains open as to the degree of accuracy of gene frequency estimates required to give accurate probability of paternity figures. This is of special concern in the HLA system, which has haplotype frequencies known to vary in populations. This paper presents computer simulation data comparing probability of paternity calculations using HLA data from California and North Carolina. Comparisons were made between geographic regions, and between blacks and whites within a geographic region. It was found that when the absolute probability of paternity is high, the average differences induced were small, but at lower probabilities the changes can be large. Differences were most pronounced between black and white populations. Examples of individual cases are given to illustrate the huge differences that can be induced in some cases by changing gene frequency.