Expanded Answers for Study Problems in: Rowland & Tozer's Clinical Pharmacokinetics: Concepts and Applications3rd edition.

Chapter 14 - Genetics

Study Problems on Page 228-229

2. Genotype is the specific gene sequence for a specific trait. Differences in genotype may or may not result in differences in phenotype. For example, there are mutations in the NAT gene in some individuals who are fact acetylators, because the mutation does not alter the expression, stability or catalytic activity of the NAT protein.

Phenotype is the functional expression of a gene. For example, blue eye and brown eyes represent different phenotypes.

Genetic polymorphism refers to a monogenic trait in which mutations are seen that result in the expression of at least two phenotypes in the population.

4. This is one of the reasons the incidence of adverse drug reactions may differ significantly between different countries. It is one of the concerns that some have with the great push to get the FDA to accept data generated in other countries for New Drug Applications. Since the incidence of genetic "defects" in xenobiotic metabolizing enzymes may differ substantially among different ethnic groups, data generated in one country may not be applicable to the population in another country. Moreover, data generated within the US, but in an exclusive ethnic group, may not provide an adequate data base for ultimate use of the drug in society - recognizing the tremendous ethnic diversity that exists in the US.

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