[Analysis of the relation of the frequency of new gene mutations for Mendelian diseases to parental age].

The effect of parental age on mutation rates of achondroplasia, neurophibromatosis, hereditary gastrointestinal adenomatosis and Duchenne muscular dystrophy loci was studied. A significant parental age effect on the occurrence of new mutations for achondroplasia and neurophybromatosis was shown. The paternal component of this parental age effect was the major factor in the occurrence of such mutations. The risk of the occurrence of new cases of achondroplasia and neurophybromatosis, as compared with their overall frequency, due to new mutations, are increased by a factor of 2 and 3, respectively, up to the paternal age of 50. The possibility of application of the data obtained in genetic counselling is discussed.