A genetic disorder is a genetic problem caused by one or more abnormalities in the genome, especially a condition that is present from birth (congenital).Most genetic disorders are quite rare and affect one person in every several thousands or millions.Genetic disorders may or may not be heritable, i.e., passed down from the parents' genes. In non-heritable genetic disorders, defects may be caused by new mutations or changes to the DNA.hether, when and to what extent a person with the genetic defect or abnormality will actually suffer from the disease is almost always affected by the environmental factors and events in the person's development.