This section provides educational information and introduces you to pharmacogenetics, the study of how your genes can influence your response to medication.

You inherited two copies of each CYP gene (i.e. CYP2D6, CYP2C9, CYP2C19 and CYP1A2), a paternal copy and a maternal copy. Each copy or allele is assigned a number preceded by an asterisk (i.e. *1 and *2). The genetic code or genotype assigned to the CYP gene identities both alleles that you have inherited (e.g. *1/*2). This standard way of denoting CYP genotypes will be used throughout this web site and the Signature Genetics™ reports.





The graphic below shows four examples that illustrate how the CYP2D6 genetic code (left panel) predicts total CYP2D6 enzyme activity (middle panel) that is associated with one of four predictive phenotypes (right panel).

• In example 1 the individual carries two fully functional (*1) CYP2D6 alleles. Both alleles contribute to the total CYP2D6 enzyme activity which in this instance, falls within the standard range. This individual can process drugs metabolized by CYP2D6 at a standard or “normal” rate and is therefore classified as an extensive metabolizer (EM).
  
  
• In example 2 one variant (*4) and one fully functional (*1) CYP2D6 allele were detected. Total CYP2D6 enzyme activity is approximately half of standard and this individual is therefore classified as an extensive metabolizer diminished (EM dim).
  
  
• In example 3 two variant CYP2D6 alleles were detected, one (*3) that is inactive, and the other (*9), partially active. Total CYP2D6 enzyme activity is barely measurable and this individual is therefore classified as a poor metabolizer (PM).
  
  
• In example 4 an additional genotype and predictive phenotype that is exclusive to CYP2D6 is shown. In this instance, more than a single copy of the CYP2D6 gene is detected on one chromosome (due to gene duplication events). As a result, the individual inherits more than 2 copies of this allele. If the allele that is duplicated is fully functional (i.e. *1, *2), total enzyme activity will be above standard range and this individual would therefore be classified as an ultra-rapid metabolizer (UM).
  

In summary, an individual's total CYP enzyme activity will affect one's ability to process certain drugs.