Final answer:
Genes serve as the molecular code instructing cells in the assembly of amino acids into proteins.
Step-by-step explanation:
Genes serve as the sequence of nitrogen-containing bases within a strand of DNA that act as a molecular code instructing cells in the assembly of amino acids into proteins. Each strand of DNA contains many separate gene sequences that code for specific proteins. These genes carry the genetic code to build an individual's body and are unique for each individual except identical twins.