The charge transfer dynamics regarding an intimate contact between graphene and single-stranded deoxyribonucleic acid (ssDNA) is investigated from DC to the THz-regime. A graphene field-effect transistor (G-FET) is immersed in ssDNA solutions where the adsorption of ssDNA is controlled in terms of absolute coverage. DC-response of the G-FET is recorded and cross-validated by observing changes in Raman spectroscopy and further investigating THz-time domain spectroscopy using a nano-slot antenna. We find very good agreement between electrical and optical approaches where the Fermi level of the ssDNA-adsorbed graphene depends on the coverage nonlinearly. The results point towards a new doping method with sub-nanoscale patterning precision on graphene and its electronic applications based on electronic junction properties.