The relation of birth rank and parental age to the phenotype distributions of 14 genetic systems in an Australian population sample.

The mean birth ranks and parental ages at birth of persons of known phenotype were determined for a sample of 421 Australian residents characterized with respect to 14 genetic systems. Sex was found to influence birth rank but no variation with parity among 38 sets of phenotypes or factors was found. Differences were observed among the maternal ages of subjects possessing MM, MN and NN phenotypes and M+ and M- factors. Persons of type PGM1 1, 2-1 and 2 possessed significantly different paternal ages; this was associated with a positive linear regression of paternal age on the PGM1-1 gene dosage. The relevance of this type of study to investigations of disorders occurring at advanced parental age is pointed out.