Functional View on DNA. Genes, Expression and Proteins In all life on earth the DNA holds the heritable information from one generation to the next. We divide the DNA sequence of nucleotides into regions: coding and non-coding regions. The coding regions hold the genes, which are transcribed and translated into proteins. Non-coding regions take part in secondary processes (see more for exam- ple in Xxxxxx et al. [2]; Xxxxxx et al. [60]). A coding region gets transcribed and translated into protein. It is flanked by specific start and stop codons (triplets of nucleotides encoding an amino acid). Flanking this, untranslated regions (UTR, “empty spaces”) can hold enhancers or structural features to influence the expression of the gene. The coding region con- sists of introns and exons. DNA is transcribed into pre-messenger ribonucleic acid (RNA) before splicing takes place. The introns are spliced (“cut”) out during xxxx- scription, so that only the exons are left for the protein. This messenger RNA gets chemically sealed by a 5’ cap and 3’ poly-A tail. Protected against degrading pro- teins, it now traverses the nucleus membrane into the intracellular space. Here ribosomes translate the mRNA into the corresponding protein. Figure 1.2 gives an overview over the expression process of proteins. The number of RNA molecules measured in a cell is known as gene expression. We assume relative differences between gene expression of different genes as a proxy for relative amounts of protein of that gene in the cell. Proteins are the active component in a cell performing the function of the gene. The functionality of the gene is to provide the information for the protein it encodes. Interaction with other genes and non-coding regions or proteins changes the expression of a gene over time. This enables a cell to respond to differing environmental circumstances in and around it. Thus, if we measure a gene to be differentially expressed under certain (changes of) circumstances, we can, with high likelihood, assign this gene (and its transcript) to respond or take part in the handling of this circumstance. Not only other genes and proteins can influence gene expression. The non cod- ing regions of DNA contain so-called biomarkers, which are sequence elements, that can influence expression. One of which is a mutation at one singular point – a single nucleotide polymorphism (SNP) – in the genetic code. If the SNP is in and around a coding region, it can influence its expression. SNPs can occur ins...
