DNA is structured like a ladder which has been Twisted to form a shape called a double helix the sides of the ladder are made of long chains of alternating sugar called deoxy ribos and phosphate and the rungs of the ladder are made of nitrogenous bases there are four possible bases which are labeled as a t c or G higher tier candidates must also learn the full name for each base a for adenine t for thyine c for cytosine and G fanine everyone must learn that there are rules on how these base pairs pair up a adenine always binds with t thyine and c cytosine always binds with G guanine this phosphate deoxy ribos sugar and nitrogenous base unit is also known as a nucleotide nucleotides are the building blocks of DNA now the bases form a genetic code which provide the instructions on the order in which the amino acids should join to form form a protein so a gene is a section of DNA which acts as a code for making a specific protein the following is higher tier only the triplet code refers to how three bases are needed to match to one specific amino acid so in the cytoplasm when a protein is being made as the code is being read in groups of three a specific amino acid is matched to that group of three and by the time the whole Gene is read out a long chain of amino acids is formed which will fold eventually into a specific protein remember a gene codes for a specific protein this is a gross simplification of the process but is all you need to know for the W JC exam