Answer to Question #121806 in General Chemistry for Gytis

Question

Describe the structure of a DNA molecule, including how individual constituents bind to each other along a length of DNA, and how two DNA strands interact with each other.

Answer 1

The DNA molecule consists of deoxyribose purine and pyrimidine bases (adenine, guanine, cytosine, thymine). 

Primary linear structure: The nucleotide residues in the DNA molecule are joined together by phosphoric acid. Phosphoric acid is always bound to the C₃ atom of a deoxyribose in one nucleotide and to the C₅ atom of a deoxyribose in the other nucleotide. This means that in DNA, phosphoric acid binds only through the 3rd and 5th carbon atoms. No branching is observed in their molecules. The following figure shows the primary structure of DNA:

The secondary structure of DNA and its double helix model were developed by D. Watson and F. Crick. According to this model, the DNA molecule consists of two polynucleotide chains that form a double helix, each of which has a common axis. these chains are bound together by hydrogen bonds formed between closely related pairs of basic molecules. hydrogen bonding occurs only between adenine-thymine and guanine-cytosine molecules. adenine and thymine are linked by 2 hydrogen bonds, and guanine and cytosine are bound by 3 hydrogen bonds. The following figure shows the secondary structure of the DNA molecule: