Feature: 1. DNA STRUCTURE: DNA molecules are formed by two polynuclear glycine chains spiraling around the same axes with the right hand helix. The main chain is an alternating arrangement of phosphate (P) and deoxyribose (D). 2. REVERSE PARALLELISM: Two polynuclear glycine chains are reverse parallel, with one strand running 5 to 3 and the other strand running 3 to 5 when viewed from one main direction. On the model, it can be seen that there are 5 to 3 chains The oxygen (0) of the deoxyribose on the top is facing upwards, while the other one is facing downwards. Phosphate (P) is also in the opposite direction. 3. STRUCTURAL DETAILS: The main chain composed of monosaccharide phosphate is located on the outer side of the helix, the base is located on the inner side, the deoxyribose is parallel to the helix axes, and the base is basically perpendicular to the axes. 4. BASE PAIRING: The bases on two chains form base pairs through oxygen bonds, and the complementary relationship between base pairs is A‑T, G‑C, and A‑T with three pairs of hydrogen bonds. The red casing on the model represents hydrogen bonding. 5. MAJOR AND MINOR GROOVE: The surface of the double helix has two obvious concave grooves, one large and deep, and the other small and shallow. They are called the major and minor groove, respectively. Specification: Item Type: DNA Structure Model Material: Plastic Model Structure: 1. Double helix with a diameter of 10A; 2. Pitch 18A, distance between adjacent base pairs 1.8A; 3. The difference in direction of adjacent bases is 360; 4. 6 pairs of base pairs per pitch; 5. The hydrogen bond length is 1.0-2.5A. Application: The product meets the national standard JY35 81 "DNA Structure Model Technical Conditions" produced by the Ministry of Education, and is suitable for teaching biology as a basic course in ordinary high schools and universities. . Package List: 1 x Model