Pharmacogenetics and Genetics Overview
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Questions and Answers

What are the building blocks of DNA and RNA called?

  • Chromosomes
  • Genes
  • Nucleotides (correct)
  • Alleles

Humans carry 46 chromosomes in each cell, which are arranged in 22 pairs.

False (B)

What is the most common form of mutation known as?

single nucleotide polymorphisms (SNPs)

The physical expression of traits is known as the ______.

<p>phenotype</p> Signup and view all the answers

Match the following terms with their correct descriptions:

<p>Gene = Instructions for features and characteristics Allele = Different forms of a gene Genotype = Genetic make-up of an organism Mutation = Change in the DNA sequence</p> Signup and view all the answers

Which base pairs are found in DNA?

<p>A-T and G-C (D)</p> Signup and view all the answers

Polymorphisms in genes have no impact on individuals' responses to medications.

<p>False (B)</p> Signup and view all the answers

What is the primary metabolism mechanism for Irinotecan that converts it into its active form?

<p>Hydroxylation by carboxylesterases (D)</p> Signup and view all the answers

Patients with reduced UGT1A1 activity are recommended a higher dose of Irinotecan.

<p>False (B)</p> Signup and view all the answers

What are the main drugs associated with Thiopurine Methyltransferase (TPMT) metabolism?

<p>Mercaptopurine, thioguanine, azathioprine</p> Signup and view all the answers

The slow acetylator phenotype is an autosomal __________ trait.

<p>recessive</p> Signup and view all the answers

Match the medication to its primary use:

<p>Isoniazid = Antibiotic Hydralazine = Antihypertensive Procainamide = Antiarrhythmic Dapsone = Antibiotic</p> Signup and view all the answers

What is the activity score (AS) for a person with no functional alleles?

<p>0 (D)</p> Signup and view all the answers

CYP2C9 is one of the least important drug metabolizing enzymes.

<p>False (B)</p> Signup and view all the answers

What is the phenotype classification for someone with an AS score of 1.0?

<p>Extensive metabolizer</p> Signup and view all the answers

CYP2D6 genotyping can assist in _____ therapy.

<p>individualized</p> Signup and view all the answers

What is the primary focus of pharmacogenetics?

<p>The study of how individual gene variations affect drug response (A)</p> Signup and view all the answers

Match the CYP2D6 activity scores with their corresponding genotypes.

<p>AS = 0 = No functional alleles AS = 0.5 = One reduced function + one non-functional alleles AS = 1.0-2.0 = One normal function + one reduced function alleles AS &gt; 2 = More than two copies of normal function alleles</p> Signup and view all the answers

Which of the following drugs is metabolized by CYP2C9?

<p>S-warfarin (C)</p> Signup and view all the answers

Pharmacogenomics is concerned with the genetic variations of individual patients.

<p>False (B)</p> Signup and view all the answers

What enzyme deficiency is associated with favism and certain drug responses?

<p>glucose-6-phosphate dehydrogenase (G6PD)</p> Signup and view all the answers

Individuals classified as poor metabolizers of CYP2C9 have two normal gene copies.

<p>False (B)</p> Signup and view all the answers

Males are more susceptible to G6PD deficiency because they inherit the condition in an _____ manner.

<p>X-linked recessive</p> Signup and view all the answers

What classification is given to a person with one normal and one reduced function allele?

<p>Intermediate metabolizer</p> Signup and view all the answers

The CYP2C9 polymorphisms significantly affect _____ dosing.

<p>warfarin</p> Signup and view all the answers

Match the following terms to their correct definitions:

<p>Pharmacogenetics = Focus on individual gene variations affecting drug response Pharmacogenomics = Study of how genes in a genome relate to the population's drug responses G6PD = Enzyme deficiency that causes acute hemolytic anemia Favism = Condition caused by eating uncooked fava beans resulting in hemolysis</p> Signup and view all the answers

How many alleles contribute to an AS score of 0.5?

<p>One reduced and one non-functional allele (C)</p> Signup and view all the answers

Which of the following is a common result of G6PD deficiency?

<p>Acute hemolytic anemia (B)</p> Signup and view all the answers

Females with one mutated G6PD gene are typically affected by the deficiency.

<p>False (B)</p> Signup and view all the answers

In what chromosome is the G6PD gene located?

<p>X chromosome</p> Signup and view all the answers

The goal of pharmacogenetics is to understand genetic ________ to individualize therapy.

<p>polymorphism</p> Signup and view all the answers

What is a consequence of CYP2C9 deficiency when receiving warfarin?

<p>Higher incidence of gastrointestinal bleeding (B)</p> Signup and view all the answers

All individuals have the same CYP2C19 polymorphisms regardless of their ethnic background.

<p>False (B)</p> Signup and view all the answers

What type of metabolisers are identified when individuals have two non-functional alleles for CYP2C19?

<p>Poor metaboliser</p> Signup and view all the answers

Individuals with CYP2C19 polymorphisms may be classified as _____, _____, _____, and _____ metabolizers.

<p>poor, intermediate, extensive, rapid, ultrarapid</p> Signup and view all the answers

Match the phenotype to their corresponding genotype for CYP2C19:

<p>Poor metaboliser = Two non-functional alleles Intermediate metaboliser = One normal + one non-functional allele Extensive metaboliser = Two normal alleles Rapid metaboliser = One normal + one increased activity allele</p> Signup and view all the answers

Which of the following describe the effect of CYP2C19 on clopidogrel?

<p>Activates the drug for efficacy (B)</p> Signup and view all the answers

Ultrarapid metabolizers have the potential for sub-therapeutic levels when taking drugs processed by CYP2C19.

<p>False (B)</p> Signup and view all the answers

What might be necessary for an intermediate metaboliser of CYP2C19?

<p>Sub-therapeutic dose may be needed</p> Signup and view all the answers

CYP2C19 polymorphisms can affect drug metabolism, with poor metabolizers potentially experiencing _____ toxicity.

<p>increased</p> Signup and view all the answers

Which group of individuals has a rarely encountered metaboliser phenotype?

<p>One non-functional + one increased function (A)</p> Signup and view all the answers

Flashcards

DNA

A double-stranded molecule carrying genetic instructions. It's made of nucleotides, which include nitrogenous bases (Adenine, Thymine, Guanine, Cytosine).

Chromosome

A tightly packed thread-like structure of DNA. Humans inherit one chromosome from each parent, forming pairs.

Gene

A specific segment of DNA that contains instructions for building proteins. These proteins determine our traits.

Allele

Different forms of the same gene. They can lead to variations in a trait like eye color.

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Genotype

The genetic makeup of an organism, which determines its traits.

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Phenotype

The observable characteristics of an organism, influenced by both genes and environment.

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SNP

Single nucleotide polymorphism, the most common type of mutation where a single base in the DNA sequence is changed.

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Pharmacogenetics

The study of how individual gene variations affect drug response and handling, focusing on pharmacodynamics and pharmacokinetics. It's often used to understand why some individuals react differently to drugs.

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Pharmacogenomics

The study of how all genes in the genome affect drug response and handling, considering both pharmacodynamics and pharmacokinetics. It's often used to develop new drugs and understand existing ones.

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Aberrant drug response

An unusual or unexpected reaction to a drug that might be caused by genetic variations leading to the study of pharmacogenetics.

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Genetic polymorphism

Variations in genes within a population that can influence drug responses.

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Individualised therapy

Treatment tailored to a patient's unique genetic makeup to optimise effectiveness and minimise side effects.

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G6PD deficiency

A genetic condition where an enzyme called glucose-6-phosphate dehydrogenase is deficient, leading to increased susceptibility to red blood cell breakdown, especially when exposed to certain drugs or substances.

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X-linked recessive inheritance

A pattern of inheritance where a mutated gene on the X chromosome is required from both parents for females to be affected, while males only need one mutated gene from their mother.

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Favism

A condition characterized by acute haemolytic anaemia triggered by consuming fava beans, often linked to G6PD deficiency.

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UGT1A1

An enzyme that metabolizes SN-38, the active metabolite of irinotecan, into inactive metabolites. It plays a role in detoxifying irinotecan and preventing toxicity.

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Primaquine

An antimalarial drug that can cause haemolytic anaemia in individuals with G6PD deficiency.

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TPMT Deficiency

A genetic condition where individuals lack sufficient Thiopurine Methyltransferase (TPMT) enzyme activity. This leads to a buildup of active thiopurine metabolites, increasing the risk of severe hematologic toxicity.

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NAT Polymorphisms

Variations in the N-Acetyltransferase (NAT) gene lead to different enzyme activity levels. This influences how quickly individuals metabolize certain drugs, affecting drug efficacy and toxicity.

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Slow Acetylator Phenotype

Individuals with two copies of the abnormal NAT gene. They metabolize drugs like isoniazid, procainamide, and hydralazine much slower than others.

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Drug-Induced Lupus

A condition where certain drugs, like hydralazine and procainamide, trigger autoimmune responses similar to lupus. This is more likely to occur in slow acetylators due to slower drug metabolism.

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CYP2D6 Genotyping

Analyzing an individual's CYP2D6 gene to determine their drug metabolism capabilities.

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CYP2D6 Activity Score (AS)

A system that assigns a score to each CYP2D6 allele based on its activity (0 = no function, 0.5 = reduced, 1 = normal).

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Poor Metabolizer

An individual with no functional CYP2D6 alleles, meaning they metabolize drugs very slowly.

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Intermediate Metabolizer

An individual with one reduced function allele and one non-functional allele, resulting in moderate drug metabolism.

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Extensive Metabolizer

An individual with two normal function alleles, leading to typical drug metabolism.

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Ultrarapid Metabolizer

An individual with more than two copies of normal function alleles, resulting in very rapid drug metabolism.

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CYP2C9

An enzyme involved in the metabolism of many drugs, including those with narrow therapeutic index (e.g., warfarin, phenytoin).

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Narrow Therapeutic Index

Describes drugs where a small difference in dosage can lead to significant side effects or toxicity.

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CYP2C9 Polymorphism

Variations in the CYP2C9 gene that affect its activity, leading to different drug metabolism rates.

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Warfarin Dosing

Adjusting warfarin dosage based on an individual's CYP2C9 genotype to personalize treatment and minimize side effects.

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CYP2C9 Deficiency

A condition where the CYP2C9 enzyme doesn't work properly, leading to higher levels of certain drugs in the body, increasing the risk of side effects.

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CYP2C9 Deficiency and Warfarin

Patients with CYP2C9 deficiency have a higher risk of bleeding when taking warfarin because the drug stays in their system longer.

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CYP2C9 Deficiency and NSAIDs

CYP2C9 deficiency can increase the risk of gastrointestinal bleeding when taking NSAIDs.

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CYP2C9 Deficiency and Sulfonylureas

CYP2C9 deficiency can increase the risk of hypoglycemia when using sulfonylureas for diabetes management.

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CYP2C19 Phenotypes

Individuals are categorized based on their CYP2C19 enzyme activity: Poor, Intermediate, Extensive, Rapid, and Ultrarapid metabolizers.

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CYP2C19 and Drug Effects

CYP2C19 can either activate (like clopidogrel) or inactivate (like amitriptyline) drugs.

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Star-Allele Nomenclature

A system used to classify different CYP2C19 alleles based on their function. Each allele is assigned a * number.

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Study Notes

Pharmacogenetics Overview

  • Pharmacogenetics is the study of how individual genes affect drug handling and response.
  • Pharmacogenetics investigates the cause of aberrant drug responses.
  • This approach is more applicable to individual patients than to a general population.
  • The goal is to personalize therapy and limit variability by understanding genetic polymorphisms.

Basics of Genetics

  • Humans inherit traits from parents encoded in DNA.
  • DNA is double-stranded, storing and transferring genetic information.
  • Nucleotides (purines and pyrimidines) are DNA building blocks.
  • DNA's four nucleobases are thymine (T), guanine (G), adenine (A), and cytosine (C).
  • RNA uses uracil (U) instead of thymine.
  • A-T and G-C base pair in DNA.
  • A-U and G-C base pair in RNA

Chromosomes and Genes

  • DNA is organized into chromosomes.
  • Humans have 46 chromosomes (23 pairs).
  • Genes are regions within chromosomes carrying instructions for traits.
  • Each person has two copies of every gene (one from each parent).
  • Genes influencing traits come in different forms called alleles.

RNA, Enzymes, and Receptors

  • RNA reads gene codes to produce enzymes and receptors.
  • Some alleles alter enzyme/receptor function and production.
  • Variations from the "normal" pattern (polymorphism) result in varied responses to medications in sub-populations.
  • Mutations are the cause of gene polymorphisms.
  • Substitution, deletion, insertion, and duplication are types of DNA mutations.
  • Single nucleotide polymorphisms (SNPs) are the most common mutation type.

Genotype and Phenotype

  • Genotype refers to the underlying genetic makeup determining traits.
  • Phenotype refers to the physical expression of traits influenced by genes and the environment.

History and Examples

  • Acute haemolytic anaemia (favism) linked to fava beans and antimalarial drugs like primaquine.
  • G6PD deficiency is an X-linked recessive genetic trait commonly affecting males.
  • Polymorphism is variability in the sequence of the genes between individuals of the same species.
  • Variations in CYP2D6 affect drug metabolism (70-80% of drug metabolism).
  • Codeine is converted into morphine, its analgesic properties affected by poor or rapid metabolisers.
  • CYP2C9 is involved in ~15-20% of CYP450 metabolised drugs.
  • CYP2C19 polymorphisms significantly affect drug metabolism. Drugs like clopidogrel and amitriptyline interact differently with CYP2C19.
  • Drug metabolism involves CYP3A4 in ~50% of cases and has wide ethnic variability.
  • UDP-glucuronyltransferase (UGT) plays a role in ~40-70% of drug metabolism.
  • Other drug metabolizing enzymes and their associated drug interactions
  • Polymorphisms in certain drug transporter genes (ABCC2, ABCG2) may impact drug effectiveness and side effects.
  • Certain OATP polymorphisms and glucose-lowering capacity of repaglinide (antidiabetic drug)
  • Several other genetic variations related to drug metabolism and responses.

Testing and Applications

  • Pharmacogenetic testing can personalize drug therapy and minimize adverse events.
  • Clinical guidelines and drug labels increasingly incorporate pharmacogenetic information to guide dosing decisions.

Summary

  • Genetic polymorphisms can significantly affect how the body handles and responds to drugs.
  • Understanding ethnic variations in these polymorphisms is critical for making appropriate therapy choices.
  • Pharmacogenetic testing is becoming critical for tailored dosing protocols.

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Related Documents

Pharmacogenetics PDF

Description

This quiz provides an overview of pharmacogenetics and basic genetics concepts. It covers how genes affect drug responses and the fundamental structure of DNA, including nucleotides and chromosomes. Understanding these concepts is crucial for personalizing therapy based on genetic information.

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