Usually a mutation is harmless if present in only one of the two or more genomes in same cell (it is said most of mutations are recessive), or even may be beneficial. Offspring of the parents who are already genetically related often inherits the same mutation in both genomes, so diseases are more frequent. If the mutation is diagnosed early in the life, sometimes diet and other similar measures may be applied, resulting a normal life later.<ref name=Al2015>{{cite journal|last1=Al Hafid|first1=N|last2=Christodoulou|first2=J|title=Phenylketonuria: a review of current and future treatments.|journal=Translational pediatrics|date=October 2015|volume=4|issue=4|pages=304–17|pmid=26835392}}</ref> | Usually a mutation is harmless if present in only one of the two or more genomes in same cell (it is said most of mutations are recessive), or even may be beneficial. Offspring of the parents who are already genetically related often inherits the same mutation in both genomes, so diseases are more frequent. If the mutation is diagnosed early in the life, sometimes diet and other similar measures may be applied, resulting a normal life later.<ref name=Al2015>{{cite journal|last1=Al Hafid|first1=N|last2=Christodoulou|first2=J|title=Phenylketonuria: a review of current and future treatments.|journal=Translational pediatrics|date=October 2015|volume=4|issue=4|pages=304–17|pmid=26835392}}</ref> |