上游充通大兽 1 A Nucleic Acid Consists of 4 Kinds of Bases SHANGHAI JIAO TONG UNIVERSITY Linked to a Sugar-Phosphate Backbone 碱基结构（5种)： NH2 嘌呤（2种) PURINES Purine Adenine Guanine 腺嘌呤 鸟嘌呤 嘧啶(3种) DNA CH3 H 5 PYRIMIDINES H Pyrimidine Thymine Cvtosine Uracil RNA 胸腺嘧啶 胞嘧啶 尿嘧啶 Figure 4.4 Purines and pyrimidines.Atoms within bases are numbered without primes.Uracil is present in RNA instead of thymine.1 A Nucleic Acid Consists of 4 Kinds of Bases Linked to a Sugar-Phosphate Backbone Figure 4.4 Purines and pyrimidines. Atoms within bases are numbered without primes. Uracil is present in RNA instead of thymine. 碱基结构（5种）： 嘌呤（2种） 嘧啶（3种） DNA RNA 腺嘌呤 鸟嘌呤 胸腺嘧啶 胞嘧啶 尿嘧啶