DNA structure:J3212

The unique plastic for allows you to assemble the model and then twist is into a double helix,instead od building it around a center post as in other models.Each of the four nitrogenous bases comes in a different unlabled color,so students can design their own base pair ciding.The model is removable from the plastic base and can be extended to its full length to demonstrate strand separation.

The DNA Molecular Model, conforming to the Standard No.J3212 set up and issued by the Ministry of Education, is designed for lecture or laboratory use in high schools and colleges. The model showing the structure of the DNA molecule enlarged 100 million times is intended for use in high schools, and 200 million times for colleges.

In the early 1950s, tow scientists at Cambridge, James Watson and Francis Crick discovered the structure of the DNA (deoxyribonucleic acid) molecule: they did this by working out the positions of the various atoms in the molecule. This model is designed on the basis of their discovery.

The DNA Molecule Structure Model demonstrates:

1. The DNA molecule is like a twisted ladder or, more technically, a double helix (two spiral strands) consisting of alternating sugar-phosphate unites, the sugar being deoxyribose.

2. The strands are antiparallel. One of the strands runs from 5’ to 3’, the other runs from 3’to 5’. On the strand running from 5’ to 3’, all the atoms of oxygen in deoxyribose face upwards; on the other, all the atoms face downwards. Phosphates also face in the opposite direction.

3. The strands consisting of sugar-phosphate units lie outside the nitrogen-containing bases. The deoxyribose unit and the supporting rod are parallel to each other and various nitrogen-containing vases are more or less ate right angles to this supporting rod.

4. These bases a re of four kinds, named “adenine”(A), “thymine”(T), “guanine”(G), and “cytosine”(C). The bases fit together as follows: A always pairs with T, and C with G. There are tow pairs of hydrogen bonds between A and T, and three between C and G. The red casings on the model represent hydrogen bonds.

5. Two grooves are on the surface of the helix. One is wider and deeper than the other.

Specifications

1. The diameter of the double helix measures 20Å.

2. 34A pitch, and 3.4 Å.

3. Neighboring bases project like the runs of a ladder towards each other at a 36 angle.

4. 10 pairs of bases exist within each pitch.

5. The length of the hydrogen bond is 2.5-3c Å.

6. The widths of the grooves are 20 Å and 14 Å.

Instructions:

1. On the model, adenine, thymine, guanine, cytosine, phosphate, and pentose units are color-coded, to make it convenient for lecture and laboratory use.

2. The model represents one and a half pitches, consisting of 16 pairs of bases.

3. The proportion of the pair of bases, A-T to that of bases G-C is 62.5 to 37.5. The order in which the asses are arranged is variable, and this is how the genes exert their effects in the organism.

4. The molecule of oxygen on the pentose is marked with “o”.

5. The hydrogen bond is marked with red color, and other bond is color-coded.

6. The assembled model supplies the necessary parts to construct complete DNA molecule. The order of the arrangement of the pairs of the bases can be changed.

7. Detailed reference material will be sent on application at a cost price.

8. Put a dust cover on the model after using.