Detailed structure of DNA
DNA polynucleotide chain has two free ends:
- 5’ end
- Free phosphate moiety at 5'-end of ribose sugar
- 3’ end
- Free 3'-OH group of ribose sugar
Watson & Crick were the first to propose the Double helix structure of DNA, based on X-ray diffraction technique.
DNA Double-helix model
- DNA is composed of two polynucleotide chains
- Sugar-phosphate forms the backbone
- Nitrogenous bases form the interior, paired through H- bonds
- Complementary base pairing is an important feature of DNA structure
- The two polynucleotide chains have anti-parallel polarity
- Two chains are coiled in a right handed fashion forming a right-handed helix
- Uniform distance is maintained between the two strands of helix
