The guanine radical cation (G •+ ) is formed by one-electron oxidation from its parent guanine (G). G•+ is rapidly deprotonated in the aqueous phase resulting in the formation of the neutral guanine radical [G (-H) • ]. The loss of proton occurs at the N1 nitrogen, which is involved in the classical Watson-Crick base pairing with cytosine (C). Employing the density functional theory (DFT), it has been observed that a new shifted base pairing configuration is formed between G(-H)• and C constituting only two hydrogen bonds after deprotonation occurs. Using the DFT method, G(-H)• was paired with thymine (T), adenine (A) and G revealing substantial binding energies comparable to those of classical G-C and A-T base pairs. Hence, G (-H) • does not display any particular specificity for C compared to the other bases. Taking into account the long lifetime of the G (-H) • radical in the DNA helix (5 s) and the rapid duplication rate of DNA during mitosis/meiosis (5-500 bases per s), G(-H)