构成核酸的结构单元分子 PURINES PYRIMIDINES NH, 0-P=0 「0-P=0 「0-P=0 0 0 0-P=0 0-P=0 0-P=0 Adenine (A 0 0 Uracil (U) 0-P=0 0-P=0 Base 0 Base 0 Base CH, Guanine(G) Thymine(T) NH OH OH OH H H H Ribonucleoside Deoxyribonucleoside Dideoxyribonucleoside triphosphate triphosphate triphosphate (NTP) (dNTP) (ddNTP) Cytosine (C)构成核酸的结构单元分子