Complex Genetic Disorders Overview
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Complex Genetic Disorders Overview

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Questions and Answers

What is a characteristic feature of complex diseases in terms of family risk?

  • They have a clear mode of inheritance.
  • They may have a raised risk in families, but the increase may be slight compared to population risk. (correct)
  • They are caused solely by environmental factors.
  • They always show a significant increase in risk compared to the general population.

    • Which of the following statements best describes the role of genetics in complex diseases?

  • All complex diseases have the same number of contributing genes.
  • Multiple genes contribute to the risk of complex diseases. (correct)
  • Complex diseases are entirely determined by environmental factors.
  • Complex diseases have a single gene responsible for their risk.

    • In assessing genetic contribution to disorders, what does heritability refer to?

  • The likelihood of a complex disease to affect all members of a family.
  • The proportion of variance in a trait caused by genetic factors. (correct)
  • The degree to which an environment can influence a disease.
  • The absolute risk of developing a disorder based on family health history.

    • What is one common approach to estimating genetic contributions to disorders?

    <p>Twin studies comparing disease concordance in monozygotic and dizygotic twins.</p> Signup and view all the answers

    Which of the following diseases is given as an example of a complex disease?

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

    Which interaction type is noted as contributing to complex diseases?

    <p>Both gene-gene and gene-environment interactions.</p> Signup and view all the answers

    What distinguishes complex diseases from simple genetic disorders?

    <p>Complex diseases are influenced by multiple factors, both genetic and environmental.</p> Signup and view all the answers

    Which genetic disorder is cited as an example of a Mendelian disease?

    <p>Cystic Fibrosis</p> Signup and view all the answers

    Which factor is NOT mentioned as contributing to complex diseases?

    <p>A single gene mutation</p> Signup and view all the answers

    What is suggested as a potential outcome of understanding the genetics behind complex diseases?

    <p>Predicting the risk of developing complex diseases.</p> Signup and view all the answers

    How is the life expectancy of individuals with Cystic Fibrosis characterized?

    <p>Approximately 40 years.</p> Signup and view all the answers

    What characterizes the inheritance pattern of Mendelian diseases like Cystic Fibrosis?

    <p>Autosomal recessive inheritance.</p> Signup and view all the answers

    What genetic condition is associated with the highest penetrance by age 70?

    <p>BRCA1 mutations</p> Signup and view all the answers

    Which of the following disorders primarily involves rare variants with Mendelian inheritance patterns?

    <p>Breast cancer</p> Signup and view all the answers

    What is the approximate carrier frequency for BRCA1 mutations in European populations?

    <p>1 in 1000</p> Signup and view all the answers

    Which of the following represents a complex disease primarily influenced by polygenic factors?

    <p>Alzheimer disease</p> Signup and view all the answers

    Which major genes are implicated in breast cancer susceptibility?

    <p>BRCA1, BRCA2</p> Signup and view all the answers

    What is the significance of the P-value threshold of 5e-08 in genetic studies?

    <p>Denotes statistical significance for association studies</p> Signup and view all the answers

    Which of the following complex diseases is primarily associated with common variants?

    <p>Rheumatoid arthritis</p> Signup and view all the answers

    When did candidate gene association studies begin, according to the historical context provided?

    <p>1950's</p> Signup and view all the answers

    What are polygenic risk scores primarily used for?

    <p>To evaluate genetic contributions to traits and diseases</p> Signup and view all the answers

    Which lifestyle factor is NOT included in the healthy lifestyle score for assessing coronary artery disease risk?

    <p>Regular exercise</p> Signup and view all the answers

    How does a high genetic risk score affect CAD risk when coupled with environmental factors?

    <p>May reduce risk if accompanied by a healthy lifestyle</p> Signup and view all the answers

    What significant threshold p-value is commonly used in genome-wide association studies for establishing statistical significance?

    <p>P=5 x 10^-8</p> Signup and view all the answers

    What does a score of 2 in the environmental risk assessment indicate?

    <p>Intermediate risk level for coronary artery disease</p> Signup and view all the answers

    What is the main limitation of genetic and environmental risk factors concerning individual risk predictions for coronary artery disease?

    <p>They are predictive only at the population level</p> Signup and view all the answers

    Which method of genotyping studies began in the 1980s and relied on genetic linkage maps?

    <p>Linkage studies</p> Signup and view all the answers

    In the study of coronary artery disease (CAD), how many SNPs were identified as associated with CAD risk?

    <p>58 SNPs</p> Signup and view all the answers

    Which of the following is true about the relationship between genetic loci and complex diseases?

    <p>Many genetic loci contribute to small percentages of disease risk</p> Signup and view all the answers

    What does the term 'penetrance' relate to in genetic studies?

    <p>The proportion of individuals with a specific genotype that show the expected phenotype</p> Signup and view all the answers

    Which of the following variants were discussed as accounting for a small proportion of the genetic component of CAD?

    <p>Rarer gene variants like LDLR and APO5</p> Signup and view all the answers

    What is the primary limitation of SNPs associated with polygenic diseases like CAD?

    <p>The risks conferred by SNPs are generally low.</p> Signup and view all the answers

    Which relative risk is associated with high environmental factors and low genetic risk for coronary artery disease?

    <p>1.90</p> Signup and view all the answers

    What major advancement in genotyping occurred in 2010?

    <p>Next Generation Sequencing studies</p> Signup and view all the answers

    In the context of predicting coronary artery disease, what role does a healthy lifestyle play?

    <p>It can mitigate the risk associated with high genetic predisposition</p> Signup and view all the answers

    Which of the following represents an accurate description of the relationship between genetics and environmental risks for coronary artery disease?

    <p>Environmental factors can enhance or diminish genetic risk factors</p> Signup and view all the answers

    The SNP rs17087335 is significantly associated with CAD. What is the odds ratio indicating its effect on CAD risk?

    <p>1.06</p> Signup and view all the answers

    What is the nature of CAD risk according to the identified SNPs?

    <p>Risk is cumulative across multiple SNPs.</p> Signup and view all the answers

    Study Notes

    Complex Genetic Disorders

    • Complex genetic disorders are influenced by numerous genetic and environmental factors, unlike single-gene disorders.
    • Common examples include Alzheimer’s disease, breast cancer, coronary artery disease, and others.

    Definitions and Characteristics

    • Complex diseases show increased familial risk, but this risk may be modest compared to the general population.
    • There is no clear inheritance pattern; multiple genes and environmental interactions play a role.
    • Examples include inflammatory bowel disease, depression, multiple sclerosis, and heart disease.

    Genetic Contribution Assessment

    • Twin studies measure disease concordance in monozygotic vs dizygotic twins to estimate heritability.
    • Heritability defines the proportion of trait variance due to genetic factors—schizophrenia has ~80% heritability.

    Spectrum of Genetic Variants

    • Disorders can range from rare Mendelian disorders to common polygenic conditions influenced by a mix of variants.
    • Well-known Mendelian disorders: cystic fibrosis, Huntington’s disease.
    • Common disorders include breast cancer (BRCA1, BRCA2), cardiovascular disease, Alzheimer’s, and autism.

    Breast Cancer Genetics

    • Major genes involved: BRCA1 and BRCA2, with rare mutations in each gene.
    • High penetrance: 65% for BRCA1 carriers, 45% for BRCA2 by age 70.
    • In Europe, BRCA1 mutation carriers: 1 in 1000; BRCA2 mutation carriers: 1 in 800.

    Evolution of Complex Disease Mapping

    • Candidate gene studies (1950s), linkage studies (1980s), genome-wide association studies (2005), and next-gen sequencing (2010s) have progressively increased resolution and understanding of genetic influences.

    Coronary Artery Disease (CAD)

    • A genome-wide association study identified 58 SNPs related to CAD through data from 60,801 cases and 123,504 controls.
    • Each SNP contributes slightly to overall risk; effects are cumulative across multiple variants.
    • An example SNP (rs17087335) shows an odds ratio of 1.06 for CAD with 21% frequency of the risk allele T.

    Polygenic Risk Scores (PRS)

    • Over 200 SNPs associated with CAD contribute low-risk profiles, combined for overall assessment.
    • PRS show promise but lack robust clinical utility due to incomplete understanding of total heritability and environmental influences.

    Interaction of Genetic and Environmental Factors

    • Both genetic predisposition and lifestyle choices contribute to CAD risk; a summary score gauges lifestyle (e.g., smoking, diet, exercise).
    • Higher genetic risk can be mitigated through healthier choices, while poor environments can elevate risk even in those with low genetic predisposition.

    Summary of Key Concepts

    • Complex diseases result from interactions of many genetic loci and environmental factors, complicating risk prediction.
    • Understanding terms such as penetrance, odds ratios, and relative risk is essential for evaluating complex disease impact.

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    Related Documents

    Complex Disease Genetics PDF

    Description

    Explore the intricacies of complex genetic disorders, which involve multiple genetic and environmental factors. This quiz covers common disorders such as Alzheimer's disease and breast cancer, highlighting their characteristics and the nature of familial risk involved.

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