 What do genes do? Roughly speaking, genes serve as templates in the synthesis of RNA molecules. The result is that the linear sequence of nucleotides in a newly synthesized RNA molecule corresponds to the linear sequence of nucleotides in the DNA segment used as the template. Different RNA molecules play different functional roles in the cell, and many RNA molecules play the role of template in the synthesis of polypeptide molecules. Newly synthesized polypeptides are linear sequences of amino acids that constitute proteins and proteins play a wide variety of functional roles in the cell and organism (and environment). The ability of a polypeptide to function in specific ways depends on the linear sequence of amino acids of which it is formed. And this linear sequence corresponds to the linear sequence of triplets of nucleotides in RNA (codons), which in turn corresponds to the linear sequence of nucleotides in segments of DNA, and this latter segment is the gene for that polypeptide.