What nucleotide will bind to G in both DNA and RNA?

The correct nucleotide that binds to guanine (G) in both DNA and RNA is cytosine (C). In the context of nucleic acid structure, the pairing rules specify that G pairs with C, forming three hydrogen bonds which contribute to the stability of the DNA double helix and RNA structures. In DNA, adenine (A) binds with thymine (T), while in RNA, adenine pairs with uracil (U). However, regardless of its form (DNA or RNA), guanine consistently pairs with cytosine due to the specific structural and chemical compatibility between these two nucleotides. This pairing is fundamental to the processes of replication and transcription, reinforcing the importance of understanding base-pairing rules in molecular biology.