Williams Syndrome Chromosomal Analysis
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Questions and Answers

What is the consequence of nondisjunction during meiosis I for chromosome 21?

  • Gametes either have two copies or none of chromosome 21. (correct)
  • All gametes contain two copies of chromosome 21.
  • All gametes contain one chromosome 21.
  • Gametes lack both chromosome 21.

    • Which of the following conditions is associated with trisomy 21?

  • Patau syndrome
  • Down's syndrome (correct)
  • Klinefelter syndrome
  • Edwards syndrome

    • Which statement is true regarding the survival rate of infants with Patau syndrome?

  • Most infants survive beyond their first year.
  • Survival rates are equal to normal infants.
  • Only 10-20 percent live past their first year.
  • Most infants die within days or weeks of life. (correct)

    • How does increasing maternal age affect the likelihood of meiotic nondisjunction?

    <p>It greatly increases the likelihood.</p> Signup and view all the answers

    What feature is associated with Edwards syndrome?

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

    What is the primary difference between aneuploidy and polyploidy?

    <p>Aneuploidy involves extra or missing chromosomes, while polyploidy involves complete sets of chromosomes.</p> Signup and view all the answers

    Which of the following describes triploidy?

    <p>A genetic disorder where an individual has three sets of chromosomes.</p> Signup and view all the answers

    What is the percentage of recognized conceptions that result in triploidy?

    <p>1% to 3%</p> Signup and view all the answers

    Which of the following chromosomal disorders is a type of structural abnormality?

    <p>Reciprocal translocation</p> Signup and view all the answers

    What phenomenon occurs due to nondisjunction during meiosis?

    <p>The occurrence of one or more missing chromosomes.</p> Signup and view all the answers

    How does mosaicism affect phenotypic expression of a chromosomal disorder?

    <p>It can lead to a varied expression of symptoms in different cells.</p> Signup and view all the answers

    Which form of chromosomal aberration involves a segment of a chromosome being reversed?

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

    Which of the following categories of genetic diseases includes aneuploid conditions?

    <p>Chromosomal Disorder</p> Signup and view all the answers

    What genetic abnormality is associated with Williams syndrome as observed in the metaphase image?

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

    Which type of chromosomal translocation involves the exchange of chromosome segments between two non-homologous chromosomes?

    <p>Reciprocal translocation</p> Signup and view all the answers

    What is a key characteristic of complete monosomies compared to complete trisomies?

    <p>Monosomies are more deleterious.</p> Signup and view all the answers

    Which chromosomes are typically viable in complete trisomy cases?

    <p>13, 18, 21, X, Y</p> Signup and view all the answers

    What factor does NOT influence the phenotype in partial aneuploidy?

    <p>Age of the individual</p> Signup and view all the answers

    Which type of inversions occur when the inverted segment includes the centromere?

    <p>Pericentric inversion</p> Signup and view all the answers

    What is the result of segmental duplications in relation to chromosome abnormalities?

    <p>They can mediate chromosomal deletions.</p> Signup and view all the answers

    Which of the following statements is true regarding the viability of complete monosomies?

    <p>Only monosomy for the X chromosome can be viable.</p> Signup and view all the answers

    What is a common feature associated with Klinefelter Syndrome?

    <p>Tall male</p> Signup and view all the answers

    What is the prevalence of Turner Syndrome?

    <p>1 in 2500 to 4000 female births</p> Signup and view all the answers

    Which condition is characterized by two bar bodies in the karyotype?

    <p>Triple X syndrome</p> Signup and view all the answers

    What cognitive characteristic is often seen in individuals with 47,XXY?

    <p>Verbal IQ reduced to low-normal range</p> Signup and view all the answers

    What is a potential behavioral phenotype for individuals with Triple X syndrome?

    <p>No significant behavioral problems</p> Signup and view all the answers

    Which syndrome is associated with delayed maturation and gonadal dysgenesis?

    <p>Turner Syndrome</p> Signup and view all the answers

    Which of the following conditions may be associated with increased risk of learning disabilities?

    <p>Triple X syndrome</p> Signup and view all the answers

    What is a common characteristic of Double Y Males?

    <p>Phenotypically normal but may be undiagnosed</p> Signup and view all the answers

    What condition is often characterized by hypothonia and delayed milestones?

    <p>Triple X syndrome</p> Signup and view all the answers

    What does mosaicism refer to in genetic terms?

    <p>Presence of two or more genetically different cell populations</p> Signup and view all the answers

    What is the main characteristic of somatic mosaicism?

    <p>Potentially symptomatic but not inheritable.</p> Signup and view all the answers

    How does germinal mosaicism differ from somatic mosaicism?

    <p>Germinal mosaicism can be inherited while somatic cannot.</p> Signup and view all the answers

    Which of the following statements about mosaic Down syndrome is correct?

    <p>It is caused by nondisjunction in the initial cell divisions.</p> Signup and view all the answers

    What defines chromosomal structural changes as balanced?

    <p>Normal complement of chromosomal material.</p> Signup and view all the answers

    What is the significance of having only about 100 documented cases of chimerism?

    <p>It suggests a rare occurrence in embryological development.</p> Signup and view all the answers

    Which of the following is a potential outcome of haploinsufficiency?

    <p>Potentially reduced gene product leading to disease.</p> Signup and view all the answers

    Which type of mosaicism is asymptomatic and not inheritable?

    <p>Somatic mosaicism.</p> Signup and view all the answers

    What chromosomal event typically leads to mosaic Down syndrome?

    <p>Nondisjunction during initial cell divisions.</p> Signup and view all the answers

    Study Notes

    Chromosomal Aberrations

    • Williams syndrome involves deletion at chromosome band 7q11.23, affecting the ELN gene.
    • Chromosome painting can depict ring chromosomes and isochromosomes, highlighting structural abnormalities.
    • Translocations occur with reciprocal or Robertsonian exchanges between chromosome segments, affecting genetic expression.

    Aneuploidy and Polyploidy

    • Euploid refers to a balanced chromosome state, typical in humans (2n = 46).
    • Aneuploidy indicates extra or missing chromosomes within a cell, common in genetic disorders.
    • Triploidy (more than two complete sets) is rare and occurs in 1-3% of conceptions, typically resulting from fertilization by two sperm.

    Nondisjunction Events

    • Meiotic nondisjunction can occur in meiosis I or II, leading to gametes with irregular chromosome numbers and potential trisomy or monosomy.
    • Increased maternal age correlates with higher risks of meiotic nondisjunction, impacting offspring.

    Common Genetic Disorders

    • Down syndrome (Trisomy 21) is a result of nondisjunction, characterized by developmental delays and specific physical traits.
    • Edward's syndrome (Trisomy 18) and Patau syndrome (Trisomy 13) present severe health challenges, often leading to early death.
    • Klinefelter syndrome (47,XXY) affects males with tall stature and infertility, while Turner syndrome (45,X) leads to short stature and webbed neck in females.

    Mosaicism and Chimerism

    • Mosaicism involves presence of genetically different cell populations resulting from mitotic errors early in development—can lead to variable phenotypic expression.
    • Chimerism consists of cells from two genetically unique zygotes, leading to distinctive cellular compositions; very few documented cases exist.

    Structural Chromosomal Changes

    • Structural rearrangements can be classified as balanced (normal chromosome material) or unbalanced (additional/missing material).
    • Individuals with chromosomal disorders may experience complications related to mosaicism and chimerism, influencing health outcomes.

    Genetic Counseling Guidelines

    • Monosomies are generally more detrimental than trisomies; complete monosomies are typically non-viable.
    • The severity of partial aneuploidies varies based on segment size, affected regions, and gene involvement.
    • Risk associated with inversions is based on their location related to the centromere and the size of the inverted segment.

    Categories of Genetic Diseases

    • Genetic diseases are classified into single-gene disorders, multifactorial disorders, and chromosomal disorders, which include both structural and numerical abnormalities.

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    Related Documents

    Genetics_13-14_Chromosomal Disorders_2024.pptx

    Description

    This quiz focuses on the chromosomal analysis related to Williams syndrome, specifically examining the deletion at chromosome band 7q11.23. Participants will explore metaphase images and the implications of the findings using the Vysis ELN region probe. Test your knowledge on the genetics and significance of these observations.

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