The function of DNA in protein coding is to store the genetic information necessary for synthesizing proteins. DNA sequences, organized into genes, are transcribed into messenger RNA (mRNA) during the process of transcription. The mRNA is then translated into proteins at the ribosome, where the sequence of nucleotides in the mRNA determines the order of amino acids in a protein. This process represents the central dogma of molecular biology, illustrating how genetic information directs the synthesis of the proteins that carry out essential cellular functions.