* Adenine (A)

* Guanine (G)

* Cytosine (C)

* Thymine (T)

These bases are the building blocks of DNA. They 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 replication and transcription of DNA, which are essential processes for the functioning of our cells and the passing of genetic information from one generation to the next.