上游究更大学 2.A Pair of Nucleic Acid Chains with Complementary SHANGHAI JIAO TONG UNIVERSITY Sequences Can Form a Double-Helical Structure 维持DNA双螺旋结构的作用力：氢键 Hydrogen bond Sugar 1 nm Sugar 3.4 nm ADENINE (A) THYMINE (T) H Sugar N Sugar 0.34nm GUANINE (G) CYTOSINE (C) Figure 4.12 Structures of the base pairs proposed by Watson and Crick.2. A Pair of Nucleic Acid Chains with Complementary Sequences Can Form a Double-Helical Structure Figure 4.12 Structures of the base pairs proposed by Watson and Crick. 维持DNA双螺旋结构的作用力：氢键