All organisms contain DNA, and every organism's DNA is made of the same four nucleotides. The differences between organisms is simply based on the order of these nucleotides. Since all organisms have the same basic, universal structure for DNA, which of these must also be universal? A) All organisms have the same proteins. B) All living things must have the same amount of DNA. C) All organisms must be genetically identical to each other. D) All codons in all organisms' DNA code for the same amino acids.