Tay-Sachs Disease Genetics Quiz
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Questions and Answers

What is the primary cause of Tay-Sachs disease?

  • Sphingomyelinase deficiency
  • GM1 ganglioside accumulation
  • Beta-hexosaminidase A deficiency (correct)
  • Beta-glucosidase A deficiency
  • In a scenario where the mother has the mutation p.Arg170Gln and the father has p.Tyr427fs, what is the expected inheritance pattern in their offspring?

  • All daughters will be affected
  • None of the offspring can be carriers
  • 1 in 4 offspring will be affected (correct)
  • All sons will be carriers
  • Which statement about X-linked recessive disorders is correct?

  • All sons of affected males are affected
  • Affected females are asymptomatic
  • Daughters of affected males will all be carriers (correct)
  • Carrier females cannot have affected offspring
  • What characterizes the mutation p.Tyr427fs associated with Tay-Sachs disease?

    <p>It causes a non-functional beta-hexosaminidase A enzyme</p> Signup and view all the answers

    How does X-linked inheritance typically affect males related via the female line?

    <p>They are typically symptomatic and affected</p> Signup and view all the answers

    What is a possible reason that females can be affected by an X-linked recessive disorder?

    <p>They have random X chromosome inactivation leading to expression in some tissues</p> Signup and view all the answers

    What type of inheritance pattern is exhibited by Myotonic Dystrophy?

    <p>Autosomal dominant</p> Signup and view all the answers

    Which of the following correctly describes the risk of an affected parent transmitting an autosomal dominant condition?

    <p>There is a 50% chance of transmission</p> Signup and view all the answers

    Which characteristic is NOT associated with autosomal dominant conditions?

    <p>Maternal inheritance only</p> Signup and view all the answers

    What does reduced penetrance refer to in the context of autosomal dominant conditions?

    <p>Not all carriers exhibit symptoms</p> Signup and view all the answers

    In autosomal dominant inheritance, what is a key feature observed?

    <p>Vertical inheritance pattern</p> Signup and view all the answers

    Which statement best represents variable expression in autosomal dominant conditions?

    <p>Expression of the condition can vary among individuals</p> Signup and view all the answers

    What is a primary purpose of genetic testing in the context of genetic disorders?

    <p>For diagnosis and confirmation of genetic disorders</p> Signup and view all the answers

    Which of the following is NOT a benefit of genetic diagnosis?

    <p>Guarantees a definitive cure for all disorders</p> Signup and view all the answers

    What key information is essential for accurate risk assessment in genetic counseling?

    <p>Confirmation of the diagnosis, family tree, and inheritance pattern</p> Signup and view all the answers

    In autosomal dominant inheritance, what is the recurrence risk to offspring from a parent with the genotype Aa?

    <p>50% chance of inheriting the dominant trait</p> Signup and view all the answers

    What does pre-implantation genetic diagnosis (PGD) facilitate?

    <p>Selection of embryos without genetic disorders</p> Signup and view all the answers

    Which condition could be confirmed through genetic testing as the only diagnostic test in some cases?

    <p>Duchenne muscular dystrophy</p> Signup and view all the answers

    What is one of the roles of genetic testing regarding family members?

    <p>To test for carrier or pre-symptomatic conditions in at-risk relatives</p> Signup and view all the answers

    Which aspect is commonly assessed to provide informed choices in future pregnancies?

    <p>Accurate familial risk estimations and management options</p> Signup and view all the answers

    What is the probability that child II.1 will inherit allele A or a from I.1?

    <p>0.5</p> Signup and view all the answers

    What is the risk of having a child affected by retinoblastoma if the parent is a heterozygote?

    <p>0.4</p> Signup and view all the answers

    In X-linked inheritance, what is the probability of a carrier female having an affected child?

    <p>1/8</p> Signup and view all the answers

    What does incomplete penetrance imply in the context of retinoblastoma?

    <p>A fraction of heterozygotes will develop the disease.</p> Signup and view all the answers

    For autosomal recessive inheritance, what is the likelihood that an unaffected sibling is a carrier?

    <p>2/3</p> Signup and view all the answers

    What characterizes variable expression in Neurofibromatosis type I?

    <p>Diverse phenotypic manifestations.</p> Signup and view all the answers

    How is the probability of a child inheriting cystic fibrosis from carrier parents determined?

    <p>1/4 due to the genetic combinations of the parents.</p> Signup and view all the answers

    What is the ratio of affected to unaffected offspring in X-linked inheritance, provided a carrier female?

    <p>1:1 for affected and unaffected.</p> Signup and view all the answers

    What is the relationship between the incidence of cystic fibrosis and the estimated carrier frequency?

    <p>Carrier frequency approximates to 2q when incidence is low.</p> Signup and view all the answers

    If the incidence of cystic fibrosis is 1 in 2500, what is the approximated carrier frequency?

    <p>1/25</p> Signup and view all the answers

    Why is it essential to establish a genetic diagnosis?

    <p>To facilitate management and treatment options.</p> Signup and view all the answers

    What is the offspring risk calculation when both parents are considered carriers?

    <p>1/150</p> Signup and view all the answers

    In the context of cystic fibrosis, what does q represent in the Hardy-Weinberg principle?

    <p>The recessive allele frequency in the population.</p> Signup and view all the answers

    How does the Hardy-Weinberg principle assist in risk calculation?

    <p>It estimates frequencies of alleles and genotypes in a population.</p> Signup and view all the answers

    What is one potential benefit of genetic diagnosis beyond establishing a clinical diagnosis?

    <p>It might predict the necessity for gene-based therapies.</p> Signup and view all the answers

    What explains the approximate value of the carrier frequency being 2pq?

    <p>With p being close to 1, 2pq simplifies to approximately 2q.</p> Signup and view all the answers

    Study Notes

    Inheritance Patterns

    • Myotonic Dystrophy follows an autosomal dominant inheritance pattern, featuring anticipation.
    • Autosomal dominant conditions arise from mutations in a single autosomal gene, usually resulting in affected individuals being heterozygous.
    • Each affected individual has a 50% chance of passing the condition to offspring, with male-to-male transmission being a key feature.

    Characteristics of Autosomal Dominant Disorders

    • Vertical inheritance ensures transmission across generations.
    • Males and females are affected equally, with affected parents capable of transmitting the disorder to both sons and daughters.
    • Key characteristics include reduced penetrance and variable expression.

    Reduced Penetrance

    • Refers to the proportion of individuals with a mutation who exhibit phenotypic symptoms, meaning not all mutation carriers show symptoms.
    • Example: In Tay-Sachs disease, mutations in the HEXA gene lead to variable expression of symptoms.

    X-Linked Inheritance

    • In X-linked recessive disorders, typically only males related through the female line are affected.
    • Carrier females have a 50% chance of passing the disorder to each son, while all daughters of an affected male become carriers.

    Genetic Diagnosis and Testing

    • Single gene testing assists in diagnosing genetic disorders, managing them, and estimating recurrence risks for families.
    • Prenatal (PND) and pre-implantation genetic diagnosis (PGD) offer reproductive options for at-risk families.
    • Accurate genetic diagnosis often limits other diagnostic procedures and provides information for future pregnancies.

    Cystic Fibrosis Examples

    • In a population with a cystic fibrosis incidence of 1 in 2500, carrier frequency approximates to 1 in 25.
    • Risk assessment shows that if both parents are carriers with no family history, the chance of having an affected child is 1 in 150.

    Key Concepts in Risk Assessment

    • Risk figures for adult-onset genetic conditions help inform family members regarding the likelihood of inherited disorders.
    • Genetic testing refines risk assessments and helps in creating informed choices concerning future pregnancies.
    • In conditions like retinoblastoma, incomplete penetrance can lead to sporadic cases, with only a portion of carriers developing symptoms.
    • Variable expression in conditions such as neurofibromatosis type I demonstrates the diversity of phenotypic traits among affected individuals.

    Overview of Hardy-Weinberg Principle

    • The Hardy-Weinberg principle aids in understanding carrier frequencies and genetic equilibrium in populations.
    • Calculating incidences and carrier frequencies assists in genetic counseling and understanding autosomal recessive inheritance patterns.

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    Description

    This quiz dives into the genetic factors associated with Tay-Sachs disease, including the inheritance patterns, specific mutations like p.Arg170Gln and p.Tyr427fs, and the characteristics of X-linked recessive disorders. Test your understanding of these complex genetic topics and their implications on offspring inheritance.

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