A triplet of bases on DNA codes for 1 codon on messenger RNA. (Transcription)
Each codon corresponds to an anti-codon on tRNA.
Each tRNA carries one amino acid, depending on its anti-codon. A codon and anti-codon are complementary.
During transcription, one strand (template) of DNA is copied to make mRNA.
The base sequence of DNA determines the sequence of amino acids in the polypeptide.
The sequence of amino acids determines how the polypeptide folds into its tertiary structure (protein), and the function of the protein.
Some of these proteins might be Transcription Factors. TF bind to promoter regions of genes, are are important in turning genes on (allow transcription). During development, genes need to be turned on in a specific, ordered, sequence. This ensures that the different body parts are assembled in the correct order during development.
Some proteins form protein hormones. These regulate development of the body from childhood to adulthood (ie. growth hormone). They might be involved in glucose metabolism (insulin, glucagon).
Proteins can also form enzymes. Enzymes are important in catalysing biological reactions in the cell.