Genotyping Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Genotyping and links to relevant pages within the course.
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| Genotyping Through Genetics Those who type as group O must have two O genes present (since both the A and B genes would have produces recognizable antigens, neither of which is present on group O cells). Therefore, in the case of an AB individual or an O individual, we can tell exactly which genes are present, or a genotype. Typing that show persons to be group A or group B reveal only one gene product and thus only a phenotype can be determined. Persons of phenotype A can be genotype AA or AO , while those of phenotype B can be genotypically BB or BO. Family studies may be done to determine the genotype of an A or B individual. Fore example, if the mating of one A and one O parent produced a group O child, the second gene present in the A parent must have been O since the child has inherited one O gene from each parent. | View Page |
| Genotype versus Phenotype Genotyping can give us a definitive profile of a given CYP450 enzyme's mutations. But since there are dozens of mutations usually associated with each enzyme, a complete characterization of a CYP450 is not always realistic. Without complete sequencing of the entire allele, it may not be possible to entirely rule out a mutation in a patient who shows none of the more common polymorphisms. If we consider the number of possible mutations and the possible presence of inducing/inhibiting substances, phenotyping for drug metabolism may sound more reasonable than genotyping. | View Page |
| TDM and PGx Can we use therapeutic drug monitoring (TDM) to assess PGx?TDM of the drug in question can also tell us a good deal about a drug's metabolism and will also take into account all the other variables at play (co-medications, diet, impaired organ function, etc.) However, unlike genotyping and probe-drug testing, therapeutic drug monitoring must be performed during therapy, not before. So, in fact, TDM is not really used to predict therapy in PGx but serves as a confirmation of PGx findings. TDM and genotyping should be considered complementary and can be used in tandem to, first, predict and then verify appropriate serum drug levels. | View Page |
| Genotype versus Phenotype Phenotyping involves measuring the metabolism of a probe drug. For example, with CYP2D6, dextromethorphan or debrisoquine can be given to a patient to see how well the drug is metabolized. Both these drugs are safe and extensively metabolized by CYP2D6. By measuring the parent drug and the metabolite in urine, the metabolic capacity of a CYP450 enzyme can be estimated. Such testing is complex and tedious, however, and has not become routine in clinical laboratories. Therefore, genotyping is likely to be the main tool that is used for assessing the PGx of a patient. | View Page |