ABSTRACT
Molecular diseases must be diagnosed by detection of abnormal molecules that cause functional disturbances of the living organisms. This can be done either by nucleic acid diagnosis which encode particular abnormal proteins or by examination of protein molecules themselves. The Eco RI enzyme will cut DNA at each site where sequence GAATTC occurs. cDNA cloning may also be used as a tool for gene analysis. A classical example represents sickle cell anemia, caused by point mutation within the beta-globin chain. Single base substitutions resulting in polymorphisms linked to mutant alleles may alter a restriction enzyme recognition site, and may be detected in the total genomic DNA by DNA blots. Restriction fragment analysis of the total DNA became a tool in constructing human gene maps. A J. effreys were the first to isolate probes of a highly polymorphic character because of a variable number of tandem nucleic acid repeat sequences.
