Photosensitizing molecules and/or metal complexes that interact with DNA via intercalation and groove binding have potential applications as molecular structural probes, as footprinting reagents and in photodynamic therapeutics. To this regard, small molecules that bind to DNA and the energetics involved in these interactions, acridine-based therapeutics, photosensitization, photodynamic therapy, phenothiazine-mediated photosensitization, DNA photocleavage reaction mechanisms and photosensitizing metal complexes are introduced in Chapter I. Next, in Chapter II, the synthesis of a photonuclease consisting of a 3,6-acridinediamine chromophore attached to four metal-coordinating imidazole rings is described. The DNA photocleavage yields, emission quantum yields, and thermal denaturation studies by this acridine-imadazole conjugate in the presence of 16 metal salts are also reported. In Chapter III is the synthesis of a bisacridine covalently tethered to a copper(II)-binding pyridine linker. Additionally, DNA photocleavage studies as well as DNA binding affinity and binding mode(s) of this bisacridine incorporating the copper(II)-binding pyridine linker are examined. The syntheses, characterization, DNA photocleavage studies, DNA thermal denaturation, and viscometric measurements of three new phenothiazinium photosensitizers are described in Chapters IV and V. Collectively, markedly enhanced DNA photocleavage yields are observed in the presence of metals (Chapters II-III) or in comparison to a parent molecule, Chapters II and IV. DNA melting isotherms show higher levels of duplex stabilization with the acridines, specifically in the presence of several metals (Chapter II-III) as well as with the phenothiazine-based ligands (Chapters IV-V). Moreover, different DNA binding modes were observed depending on metal complexation (Chapter III) and nucleic acid structure (Chapter IV). Finally, Chapter VI describes a small project implemented as a National Science Foundation pedagogical laboratory exercise in which a non-invasive procedure for DNA isolation from human cheek cells was utilized with the polymerase chain reaction to amplify alleles encoding a single nucleotide polymorphism involved in normal human color vision.