What gene diseases can you name? What are their reasons?

Gene diseases include numerous metabolic disorders (carbohydrates, lipids, amino acids, metals, etc.), as well as hereditary deafness, optic atrophy, six-fingered, short-fingered, and many other pathological signs.
Most gene diseases are associated with mutations in certain genes, which leads to a change in the structure and functions of the corresponding proteins and appears phenotypically. For example, phenylketonuria is caused by a defect in a gene that encodes an enzyme that converts the phenylalanine amino acid into another amino acid, tyrosine. The cause of hemophilia is a decrease or violation of the synthesis of one of the coagulation factors.