The structure of DNA

The structure of DNA

DNA is made up of:

• Two polynucleotide strands which form a double helix
• A pentose sugar which is deoxyribose
• Four bases - two purines which are adenine and guanine and two pyrimidines which are cytosine and thymine
• The deoxyribose and phosphate groups form the 'backbone'
• The bases on the inside face each other and guanine is to cytosine and thymine is to adenine, these are complementary base pairings. 
• Hydrogen bonds join the bases in their complementary pairs and these maintain the shape of the double helix.

A DNA molecule is very long and thin. It's tightly coiled within a chromosome and the double helix is 2nm or 2.0x10^7cm. A DNA molecule in a human chromosome is about 85mm long. Nucleotides in one strand are arranges in the opposite direction to the other strand therefore the strands are antiparallel. 

DNA and its functions

DNA is suited to it's functions for several reasons, including:

• It's a very stable molecule, its content passes from generation to generation without changing
• It's a very large molecule which…