Genetics Chapter 5 Quiz
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Questions and Answers

What does reduced penetrance refer to in genetic disorders?

  • The presence of the mutation in one or both chromosomes.
  • The likelihood that a gene mutation will result in the expression of disease. (correct)
  • The ability of a gene to change its expression over time.
  • The variability in symptom severity among individuals with the same mutation.
  • What role does a pedigree play in understanding genetics?

  • It is used exclusively for diagnosing mitochondrial disorders.
  • It helps in tracking environmental factors affecting genetics.
  • It determines the exact location of mutations on chromosomes.
  • It assists in visualizing inheritance patterns across generations. (correct)
  • Which of the following describes expressivity in single-gene disorders?

  • Different mutations always produce the same phenotype.
  • Variability in severity of symptoms among individuals with the same gene mutation. (correct)
  • Mutations that are inherited from one parent only.
  • Completely penetrant mutations always result in severe symptoms.
  • What can be concluded about single-gene disorders based on mutation variability?

    <p>Different mutations can lead to the same disease with varying severity.</p> Signup and view all the answers

    What is a key method used in genetic testing to confirm mutation presence?

    <p>PCR and sequencing.</p> Signup and view all the answers

    What is the effect of mutations in the LDLR gene on LDL-C levels?

    <p>They decrease the ability of cells to clear LDL-C, leading to higher levels.</p> Signup and view all the answers

    How do mutations in the APOB gene affect cholesterol levels?

    <p>They impair LDL clearance, raising cholesterol levels.</p> Signup and view all the answers

    What role does PCSK9 play in regulating LDL clearance?

    <p>It increases LDL receptor degradation.</p> Signup and view all the answers

    What is the consequence of mutations in the PCD enzyme?

    <p>Deficiency of tetrahydrobiopterin (BH4).</p> Signup and view all the answers

    What effect do mutations in DHPR have on BH4?

    <p>They cause BH4 deficiency.</p> Signup and view all the answers

    How many α1 and α2 chains are present in a normal collagen molecule?

    <p>2 α1 chains and 1 α2 chain.</p> Signup and view all the answers

    What is typically observed in muscle with fatty and connective tissue infiltration?

    <p>Enlarged or hypertrophied muscles.</p> Signup and view all the answers

    What happens to collagen production when there are mutations affecting α1 and α2 chains?

    <p>There is either too much collagen or abnormally formed collagen.</p> Signup and view all the answers

    What does heritability represent in a population?

    <p>The proportion of phenotypic variation due to genetic variations</p> Signup and view all the answers

    Which statement best describes the scope of heritability?

    <p>It applies only to individuals within specific populations.</p> Signup and view all the answers

    What is the significance of a relative risk greater than 1 in heritability studies?

    <p>The event is likely to occur more frequently</p> Signup and view all the answers

    How is heritability typically estimated?

    <p>Through the examination of phenotype and genotype associations</p> Signup and view all the answers

    Why can't heritability be used to predict genetic differences between races?

    <p>Because it is based on individual differences within a single population</p> Signup and view all the answers

    What is a key limitation of interpreting heritability scores?

    <p>It does not account for environmental influences.</p> Signup and view all the answers

    Which of the following best defines the concept of heritability?

    <p>The ratio of genetic to environmental influences on variation</p> Signup and view all the answers

    What term describes the genetic factors that contribute to heritability measurements?

    <p>Genetic variation</p> Signup and view all the answers

    What is the primary genetic cause of Osteogenesis imperfecta?

    <p>Mutations in the COL1A1 or COL1A2 gene</p> Signup and view all the answers

    What distinguishes the functions of PAR1 and PAR2?

    <p>PAR1 is involved in pairing during meiosis and contains more genes</p> Signup and view all the answers

    Which statement is accurate regarding sex-linked inheritance patterns?

    <p>Sex-linked traits do not skip generations</p> Signup and view all the answers

    Which of the following accurately represents a characteristic of pseudo-autosomal regions (PARs)?

    <p>PARs allow for exchange of genetic material between X and Y chromosomes</p> Signup and view all the answers

    What is true about a compound heterozygote?

    <p>They have two different mutated alleles of the same gene from each parent</p> Signup and view all the answers

    In genetic terms, what does recombination in PARs ensure?

    <p>It allows proper segregation of chromosomes during meiosis</p> Signup and view all the answers

    How do sex-linked traits differ from autosomal dominant traits?

    <p>They are equally likely to appear in both genders</p> Signup and view all the answers

    What would be the chance for a son of a female carrier of a sex-linked trait to inherit the trait?

    <p>50 percent</p> Signup and view all the answers

    What best describes heritability?

    <p>The genetic contribution to variations in traits within a specific group of people.</p> Signup and view all the answers

    Which inheritance pattern incorporates both genetic and environmental influences?

    <p>Multifactorial inheritance</p> Signup and view all the answers

    Which of the following is an example of a disease associated with polygenic inheritance?

    <p>Diabetes 1</p> Signup and view all the answers

    Which statement about children of identical twins is accurate?

    <p>They have a higher genetic relatedness compared to cousins of non-identical twins.</p> Signup and view all the answers

    Which of the following is an example of an autosomal recessive disorder?

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

    What is the primary inheritance pattern for Myotonic dystrophy?

    <p>Pseudo-autosomal inheritance</p> Signup and view all the answers

    How is heritability interpreted when it is low?

    <p>Environmental influences play a significant role in the trait.</p> Signup and view all the answers

    What type of study helps determine the genetic contribution to traits by comparing twins?

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

    Which disorder is characterized by genomic imprinting?

    <p>Prader-Willi syndrome</p> Signup and view all the answers

    Which of the following statements about autosomal dominant disorders is true?

    <p>Affected individuals have a 50% chance of passing the disorder to their children.</p> Signup and view all the answers

    Which trait aspect is primarily affected by environmental influences?

    <p>Traits with low heritability</p> Signup and view all the answers

    What distinguishes multifactorial inheritance from other types of inheritance?

    <p>It incorporates environmental factors alongside multiple genes.</p> Signup and view all the answers

    Which disorder is NOT classified as X-linked?

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

    In dyschondrosteosis, the gene responsible for the disorder is located on which chromosome?

    <p>Chromosome 12</p> Signup and view all the answers

    What inheritance pattern is most commonly associated with Fragile X syndrome?

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

    Which of the following is a characteristic of uniparental disomy?

    <p>Causes imprinted disorders.</p> Signup and view all the answers

    Study Notes

    Single-Gene Disorders

    • Single-gene disorders are caused by mutations in a single gene.
    • Mendelian inheritance follows patterns described by Gregor Mendel.
    • Each inheritance type has a specific pattern across generations.
    • Knowledge of family history and inheritance type aids in identifying carriers and understanding risk.
    • Several different mutations can result in the same disease, but with varying degrees of severity.
    • Penetrance is the likelihood a gene mutation will result in disease expression.
    • Expressivity is the variation in severity of disease symptoms among individuals with the same gene mutation.
    • Genetic testing (PCR and sequencing) confirms mutation presence and guides diagnosis.

    Objectives

    • Describe how genes are inherited, the types and extent of genetic variation seen in the human genome, and how these variations affect disease states and the diversity of normal variation.
    • Obtain a family history and draw and interpret a pedigree.
    • Perform pedigree analysis and identify the inheritance patterns.
    • Explain and identify non-Mendelian mechanisms: reduced penetrance, variable expressivity, uniparental disomy, epigenetics, mosaicism, genomic imprinting, and unstable repeat expansion.

    Single-Gene Inheritance (Mendelian Inheritance)

    • Refers to genetic disorders or traits controlled by mutations in a single gene.
    • Follows inheritance patterns described by Gregor Mendel.

    Characteristics of Patterns of Transmission

    • Each inheritance type has a specific pattern across generations.
    • Knowledge of family history and inheritance type aids in identifying carriers and understanding risk.

    Mutation Variability

    • Even though a single gene primarily causes these diseases, several different mutations can result in the same disease but with varying degrees of severity and phenotype.

    Key Genetic Concepts

    • Penetrance: Likelihood that a gene mutation will result in disease expression.
    • Expressivity: Variation in severity of disease symptoms among individuals with the same gene mutation.
    • Genetic Testing: Methods like PCR and sequencing to confirm mutation presence and guide diagnosis.

    Single-Gene Disorders (Important Facts)

    • Individual mutant genes cause the disorder (monogenic).
    • The mutation can be present on one or both chromosomes.
    • Frequency is as high as 1/500.
    • Affects about 0.2% of the population.
    • Incidence in live births is about 0.36%.
    • Hospitalized children are affected 6-8%.
    • Mitochondrial disorders are included.

    Pedigree

    • A family tree that tracks traits or conditions through generations.
    • Uses symbols and lines to represent relationships.

    Types of Single-Gene Inheritance Patterns

    • Autosomal Recessive: Requires two mutated genes (one from each parent) to manifest.
    • Autosomal Dominant: Requires only one mutated gene from either parent to manifest.
    • X-Linked (Sex-Linked): Caused by mutations on the X chromosome, primarily affecting males.

    Atypical Patterns of Inheritance

    • Incomplete Dominance: When an individual inherits two different forms of a gene, resulting in a blend of traits.
    • Codominance: Both alleles are fully expressed in the offspring.
    • Mitochondrial Inheritance: Inherited only from the mother.
    • Anticipation: A genetic disorder becoming apparent earlier and/or more severe in subsequent generations.
    • X-Inactivation: One X chromosome is randomly turned off in each cell of a female.

    Autosomal Dominant Inheritance (Example Diseases):

    • Neurofibromatosis type 1
    • Familial hypercholesterolemia
    • Achondroplasia

    X-Linked Inheritance (Example Diseases):

    • Muscular dystrophy
    • Hemophilia
    • Hypophosphatemic rickets

    Compound Heterozygote

    • A person who has two different mutated alleles for a single gene.
    • These mutations affect the gene's ability to work properly, and therefore cause the same disease.

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    Description

    Test your knowledge on key concepts from Genetics Chapter 5, including reduced penetrance, expressivity, and the significance of pedigrees in studying genetic disorders. Additionally, explore methods used in genetic testing to identify mutations. Challenge yourself with these essential questions on single-gene disorders!

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