A genomic revolution is underway across healthcare, with some disciplines further ahead in its application than others, for example pharmacogenomics. In the past information was available relating to alterations in individual genes leading to single gene conditions, genomic information considers how an individuals’ genome and their environment increase or decrease their risk of a particular health concern, an individuals’ response to a drug or treatment, the development of a particular cancer and how infections spread. This revolution in available information has been made possible owing to the availability of techniques to sequence the whole of the human genome
The human genome sequence was completed in 2003 by the international human genome project working from research centres in the US, UK, Japan, France, Germany, Spain and China. Since then techniques have continued to rapidly improve and the cost of sequencing has dramatically come down in price.
Research has also taken place using large genome-wide association studies (GWAS) involving thousands of people’s DNA. These studies have shown associations between specific genetic loci and particular diseases or susceptibility to disease (for example, chronic multifactorial conditions such as hypertension and diabetes) and phenotypic characteristics (for example, overweight and obesity).
Whether or not a patient with a gene alteration associated with a specific disease will go on to develop that disease is often dependent on external factors such as diet (and individual components within the diet), lifestyle and the environment. The potential influence of dietary components on phenotypic outcome has led to the field of nutritional genomics (Bidlack 2012).
If you would like a reminder of how DNA makes proteins, see below.
When a gene receives a signal to produce a protein, it goes through a process known as gene expression. This involves a complex set of actions that includes the transcription (copying DNA sequence into mRNA) and translation (making the proteins from the RNA) of the coding region of the DNA. The diagram below is a simplified illustration of the whole process of protein production.
The DNA double helix molecule is unravelled, and each separate strand is then copied and messenger RNA (mRNA) produced. mRNA is a transitory molecule that is able to pass out of the nucleus of the cell and into the cytoplasm, which then allows the next stage of gene expression to occur, translation.
As part of the complex process of making mRNA from the DNA sequence proteins called transcription factors are required, such as PPAR. Transcription factors modulate gene expression; in other words, gene expression is controlled by the availability and activity of transcription factors. Many transcription factors are known to require nutrients or bioactive non-nutrients in the diet in order for them to work effectively, such as essential fatty acids. The expression of protein coding genes is also regulated by a large number of RNA molecules
The mRNA is then modified to remove non-coding parts of the instruction an action known as splicing. At the ribosome, the sequence of bases in the mRNA is read in groups of three bases, known as codons. Each codon specifies a particular amino acid or an instruction to stop.
These amino acids are joined together in the order of the codons to form a polypeptide chain. This process is known as translation. It is enabled by small molecules called transfer RNAs (tRNAs), which are each specific for one of the codons and carry the corresponding amino acid in order to incorporate it into the growing polypeptide chain. Once the polypeptide chain has been made it can be further modified to produce the final three dimensional structure of the protein.