DNA double helix structure and function

• DNA is made up of two anti-parallel polynucleotide chains joined together through hydrogen bonds between complementary base pairs. The two chains then twist around each other to form a double helix.
• DNA is a stable molecule which allows genetic information to be passed from generation to generation without change unless through mutation.  
• DNA is a large molecule which allows it to carry a large quantity of genetic information 
• Adenine always pairs with Thymine ( A = T  )
• Guanine always pairs with cytosine (C =G) 
• Hydrogen bonds which join the two strands are weak bonds which allows easy separation during DNA replication and protein synthesis
• There are 2 Hydrogen bonds between A & T and 3 H bonds between C & G 
• The strong phosphodiester bonds protect the nitrogen containing Bases - which form the code - in the centre of the molecule.