Final answer:
Genetic diseases that do not demonstrate heritability are typically caused by recessive phenotypes. Autosomal recessive disorders, like cystic fibrosis and Tay-Sachs disease, require two copies of the faulty gene to be expressed, while autosomal dominant disorders, like Huntington's disease, manifest with just one copy.
Step-by-step explanation:
Diseases that are not selected for heritability are usually the result of recessive phenotypes rather than dominant ones. An example of autosomal recessive disorders includes conditions like cystic fibrosis and Tay-Sachs disease. These disorders are typically only expressed when two carriers have offspring since carriers have the recessive allele but do not express the trait due to the presence of a normal dominant allele. On the contrary, autosomal dominant disorders such as Marfan syndrome and Huntington's disease need only one copy of the faulty gene to be expressed. Additionally, some disorders, such as hemophilia and color blindness, follow an X-linked recessive inheritance pattern where males are more frequently affected due to having only one X chromosome.