Pharmacogenetics refers to the study of genetic influences on an individuals response to drugs. In pharmacogenetics, the analysis of a specific gene or group of genes may be used to predict response to a drug or class of drugs.
On the other hand, the study of all genes that play a role in drug responses is referred to as pharmacogenomics. It also includes the study of how analysis of total genome may provide more knowledge on genes in the search for drug targets and all key factors in drug reactions.

The effect of a specific dose of a specific drug would differ between individual recipients. Some persons may be very responsive to a particular drug; others may be non-responsive. Some may show a partial response while in some others there may be adverse drug reactions. There are many contributing factors to such variations in drug response such as gender, body mass, age, diet, the presence of other medications or particular disease types and exposure to certain chemicals or toxins such as cigarette smoke. In addition to these, genetic factors also influence drug response.
Pharmacogenomics involves whole genome sequencing (WGS) and investigating all variations in the entire genome.

Pharmacogenetics involves targeted gene panels identifying variations in a predetermined selection of gene(s).
Whole genome sequencing provides information on the full spectrum of variations by sequencing the whole genome. Pharmacogenetics (gene(s)-specific drug response testing) provides actionable results and helps clinicians to tailor medications to suit patients needs. It emphasises on particular genes and how they affect an individuals response to a specific drug. Whereas WGS can also provide actionable results, it is not usually required by clinicians to provide actionable results. It is not necessary to have the entire genome analysed before useful results for patients treatment are obtained. Even in cancer treatments, it is not usually required as it is a specific gene(s) that are known to influence the metabolism of cancer drugs.

Whole genome sequencing (WGS) or targeted gene panels promises a potential future standard of healthcare and medicine in general. It might not be necessary to provide actionable results, but it can aid immensely research in genetics and provide never-before-seen information about variations in the genome. WGS and its applications is primarily a promising technology with the challenge of storing and making sense of the vast amount of data (6.4 billion base pairs in one human genome; 3.2 in the reference genome). It is an expensive venture, but in recent times we have begun to see the cost reduction.

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