In a eukaryotic cell's genome, there are billions of nucleotides arranged in a linear sequence; however, these cells only use a small portion of this genetic material. Some of the DNA that is not used for genes is non-coding sequences or gene duplication. In non-coding sequences, the sequences do not eventually lead to a functional polypeptide for a particular cell. Non-coding sequences are also known as introns. Tips or caps on genes also contribute to the enormous amount of DNA. Tips prevent gene degradation by enzymes which would, without the tips, destroy the genes so that they would not lead to a functional polypeptide.

The flow of genetic information flows from DNA to making the gene available for transcription to hnRNA to mRNA to the linear organization of a polypeptide into a functional protein. Factors which can control the expression of the genetic information can occur at any...