DNA

• DNA is a complex molecule that contains all the information necessary to build and maintain an organism. It is the carrier of the genetic code and provides instructions for coding specific polypeptides (primary protein structure).
• DNA has a double-helix (spiral) structure consisting of two complementary strands each made up of a repeating series of nucleotides.
• Each DNA strand is comprised of deoxyribose sugar-phosphate backbones with the complementary base pairs binding the double-stranded DNA molecule together.
• The chemical structure of the nitrogenous bases means they form specific complimentary base pairs.The complementary base pairs are: A pairs with T G pairs with C
• The DNA strands are held together by weak hydrogen bonds between the paired bases. A double bond between A and T and a triple bond between G and C
• In the structure of a DNA double helix, the bonds between nitrogenous bases are always a purine to a pyrimidine.
• The bases always attach to the deoxyribose sugars in the backbone and there is always a phosphate between the two deoxyribose sugars in the backbone.
• The two complementary strands have an antiparallel arrangement meaning they run parallel to each other in opposite directions.
• Therefore, one strand runs from the 5’ to 3’ end and the other runs from 3’ to 5’ end.