**5.2 Drug design for common allele diseases**

These are the diseases of old age people. Nowadays, people rarely die of infectious diseases. Because of the availability of a variety of antibiotics, today, most people live beyond age 70 years and some of them go on living beyond 80 years of age. Those who live beyond 70 are faced with three major old age diseases, which are responsible for causing the death of most patients during their lifetime and they are cancers, cardiac diseases, and Alzheimer. These are genetic diseases and could be treated either by gene therapy (using CRISPER technology by replacing bad gene with the good gene using CRISPER-Cas9) or by drug therapy. There are about 3000 monogenic diseases and could be treated by replacing the defected gene with good gene, that is, by gene therapy or designing drugs to shut off the bad genes that is drug therapy. Gene therapy cannot be applied to treat multiple genetic defects such as Alzheimer, cancer, and cardiovascular diseases. Drug therapy could be used to develop novel treatments. Recently completed 1000 Human Genome Project identify with precision and accuracy the genes responsible for causing these diseases. It is now possible to design drugs to shut off these genes and save human life. Genes code for proteins and a mutated gene codes for abnormal proteins resulting in these diseases.
