ABSTRACT
The mitochondrial genome has been sequenced and mapped, and the far larger nuclear genome is being mapped piece by piece. When insufficient purines and pyrimidines are provided, cell replacement, growth, and tissue repair are possible. Depending on the binding protein and the nutrient bound to it, transcription is either enhanced or inhibited and indeed cell types may differ because of these proteins. A number of nutrients bind to nuclear receptors that in turn bind to DNA, and together these nutrient-bound receptors have effects on transcription. As mentioned in the section on transcription, newly formed mRNA is edited prior to leaving the nucleus. In iron deficiency, the mRNA start site for ferritin translation is covered up by an iron-responsive protein. The sequence of amino acids in each protein synthesized by the body is determined from a subunit of the DNA molecule known as the gene.
