Hereditas 1989; 11(1):31. A human twin study using the monozygo-tic dizygotic comparison method was under-taken. the accuracy of the zygosity diagnosiswas more than 98 per cent. twenty-two pairsof normal monozygotic twins had an intraclass Hereditas 1989; 11 (1): 31. A human twin study using the monozygo-tic dizygotic comparison method was under-taken. The accuracy of the zygosity diagnosis was more than 98 per cent. Twenty-two pairs of normal monozygotic twins had an intraclass