Figure 1 (A) A schematic gene. A strand of DNA contains genes, areas that regulate genes, and areas that either have no function. A gene contains the coded information to make a protein. The code is written in the DNA sequence of nucleotides (bases): CTAG. The genetic information contained in a strand of DNA is determined by the sequence of the bases. (B) Gene expression. RNA polymerase (•) binds to the promoter region of the gene. Then RNA is produced (a faithful copy of the genetic code of the gene: a process known as transcription) to produce the messenger RNA, which is then converted into an amino acid chain by reading of the RNA code (translation). The final amino acid chain is then processed by the cell to produce a functional protein. (C) Functional single nucleotide polymorphism. A single nucleotide change (▴) in the DNA sequence may alter gene expression by changing levels of the protein produced or activity of the protein. Here the change in the single nucleotide or base occurs in the promoter area of the gene (the area where the RNA polymerase binds) and thus affects messenger RNA production, leading to altered protein levels and activity.