* Adenine (A)

* Guanine (G)

* Cytosine (C)

* Thymine (T)

These bases pair up in a specific way: Adenine always pairs with Thymine (A-T), and Guanine always pairs with Cytosine (G-C). This pairing is crucial for the structure and function of DNA.

In RNA, Thymine is replaced by Uracil (U), so the base pairs are A-U and G-C.