Final answer:
The four nitrogen bases in DNA are adenine, thymine, cytosine, and guanine, with adenine and guanine being purines and cytosine and thymine being pyrimidines.
Step-by-step explanation:
The four nitrogen bases found in DNA are adenine, thymine, cytosine, and guanine. These bases are essential components of nucleotides, which are the building blocks of DNA. Adenine (A) and guanine (G) are classified as purines, which have a double-ring structure, while cytosine (C) and thymine (T) are classified as pyrimidines, featuring a single-ring structure. It's important to note that in RNA, thymine is replaced by uracil (U), another pyrimidine. To remember the pyrimidines, the mnemonic 'cut pyramid' can be used, where 'c' stands for cytosine, 'u' for uracil, and 't' for thymine, with 'pyramid' reminding us of pyrimidines.