The instructions for building proteins necessary for all life functions are coded within an organism's genetic code. the genetic code of an organism consists of codons, or sequences of three nucleotides, that each code for a specific amino acid. amino acids are the building blocks of proteins. the amino acids coded by specific codons a. differ between members of different species. b. are almost universal among all living things. c. differ between plants and animals. d. are different for every organism on earth.