Chromosomal Aberrations Overview
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Questions and Answers

What is one of the main classifications of chromosomal aberrations?

  • Functional aberrations
  • Physiological aberrations
  • Behavioral aberrations
  • Structural aberrations (correct)

    • Which condition is an example of aneuploidy?

  • Translocation
  • Tetraploidy
  • Down syndrome (correct)
  • Triploidy

    • Which maternal factor is associated with an increased risk of chromosomal aberrations?

  • Low vitamin D levels
  • High blood pressure
  • Advanced maternal age (correct)
  • Maternal smoking

    • What type of structural aberration involves losing a segment of a chromosome?

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

    Which infection is known to cause fragmentation of chromosomes?

    <p>German measles</p> Signup and view all the answers

    Which of the following best describes polyploidy?

    <p>Three or more complete sets of chromosomes</p> Signup and view all the answers

    What is a common chemical agent that increases the risk of chromosomal aberrations?

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

    What is not considered a type of structural chromosomal abnormality?

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

    What is Turner syndrome characterized by at the chromosomal level?

    <p>45 chromosomes with a missing X chromosome</p> Signup and view all the answers

    Which of the following does NOT occur in polyploidy?

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

    What is the karyotype for Klinefelter syndrome?

    <p>47, XXY</p> Signup and view all the answers

    Which factor can lead to non-disjunction and subsequent chromosomal abnormalities?

    <p>Drugs affecting microtubule systems</p> Signup and view all the answers

    What is the chromosome composition in individuals with super female syndrome?

    <p>47, XXX</p> Signup and view all the answers

    In the context of chromosomal abnormalities, what does di-spermy refer to?

    <p>Fertilization of an egg by two sperm</p> Signup and view all the answers

    Which condition is characterized by cells having three sets of chromosomes?

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

    What is a common feature seen in individuals with Turner syndrome?

    <p>Limb edema</p> Signup and view all the answers

    What is the result of non-disjunction during meiosis I?

    <p>2 normal and 2 abnormal daughter cells</p> Signup and view all the answers

    Which syndrome is caused by a trisomy of chromosome 21?

    <p>Down syndrome</p> Signup and view all the answers

    Which of the following is a characteristic associated with Klinefelter syndrome?

    <p>Presence of Barr body</p> Signup and view all the answers

    What cellular event leads to the condition of mosaicism?

    <p>Non-disjunction during early mitotic divisions</p> Signup and view all the answers

    What is the chromosomal make-up of a male with Klinefelter syndrome?

    <p>47, XXY</p> Signup and view all the answers

    What is a potential outcome of anaphase lag during cell division?

    <p>Micronucleus formation</p> Signup and view all the answers

    What condition is associated with the presence of two Barr bodies?

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

    What is a feature of Down syndrome's chromosomal makeup?

    <p>47 chromosomes total</p> Signup and view all the answers

    What is the main characteristic of reciprocal translocation?

    <p>It requires breakage and exchange between non-homologous chromosomes.</p> Signup and view all the answers

    Which type of translocation is characterized by the loss of short arms from two chromosomes?

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

    How many chromosomes does a person typically have after a Robertsonian translocation?

    <p>45 chromosomes</p> Signup and view all the answers

    Which of the following is an example of a disease associated with reciprocal translocation?

    <p>Chronic myeloid leukemia</p> Signup and view all the answers

    What is meant by para-centric inversion?

    <p>It involves two breaks in one arm without involving the centromere.</p> Signup and view all the answers

    In the process of insertion, which scenario applies?

    <p>A segment of one chromosome is translocated and inserted into a different region of the same chromosome.</p> Signup and view all the answers

    What is the primary consequence of inversion on genetic material?

    <p>It reverses the position of the segment within the same chromosome.</p> Signup and view all the answers

    Which chromosomes are most frequently associated with Robertsonian translocation?

    <p>Chromosomes 14 and 21</p> Signup and view all the answers

    What characterizes an iso-chromosome?

    <p>It has mirror image arms.</p> Signup and view all the answers

    What is the primary feature of a duplication in a chromosome?

    <p>It involves the presence of two copies of a segment.</p> Signup and view all the answers

    What is a defining characteristic of a dicentric chromosome?

    <p>It contains two centromeres.</p> Signup and view all the answers

    What causes the fragile X chromosome to be identified?

    <p>An unusual narrow site seen under a microscope.</p> Signup and view all the answers

    Which prenatal screening method involves extracting amniotic fluid?

    <p>Amniocentesis.</p> Signup and view all the answers

    What happens to a dicentric chromosome during mitosis?

    <p>It is torn apart and its parts are divided.</p> Signup and view all the answers

    Which chromosomal abnormality is known to feature both deletion and duplication?

    <p>Iso-chromosome.</p> Signup and view all the answers

    Which of the following best describes the instability of a dicentric chromosome?

    <p>It is unstable and torn apart during mitosis.</p> Signup and view all the answers

    What type of diagnostic test involves a small sample of blood taken from the umbilical cord?

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

    Which chromosomal alteration involves a segment being reversed end to end?

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

    Cri-du-chat syndrome is associated with which type of chromosomal alteration?

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

    Which of the following syndromes is a structural chromosomal anomaly?

    <p>Wolf-Hirschhorn syndrome</p> Signup and view all the answers

    Para-centric inversion involves which of the following?

    <p>Two breaks occurring in the same chromosome arm</p> Signup and view all the answers

    Which method analyzes the chromosomes for structural changes?

    <p>FISH technique</p> Signup and view all the answers

    What is the primary purpose of chorionic villus sampling?

    <p>To obtain fetal DNA for genetic testing</p> Signup and view all the answers

    Which of the following best describes translocation?

    <p>The movement of a segment to another chromosome</p> Signup and view all the answers

    Study Notes

    Chromosomal Aberrations (Abnormalities)

    • Definition: Disorder involving morphological or numerical alteration in single or multiple chromosomes. This affects autosomes, sex chromosomes, or both.
    • Numerical aberrations: Abnormality in the number of chromosomes.
    • Structural aberrations: Abnormality in the structure of chromosomes.

    Causes Increasing the Risk of Chromosomal Aberrations

    • Environment:
      • Exposure to radiation (X-rays).
      • Chemical agents (formaldehyde, pesticides, food preservatives, tobacco).
      • Cytotoxic drugs (cholchicine, tetracyclines).
      • Maternal age (older pregnancy increases risk of non-disjunction).
      • Presence of chromosomal imbalance in family members (family tendency).
    • Medical conditions:
      • Autoimmune diseases.
      • Hypothyroidism.
      • Infections (e.g., German measles, causing fragmentation).

    Numerical Aberrations

    • A- Aneuploidy: An abnormal number of chromosomes (not a multiple of the haploid number).

      • 1- Trisomy (2n+1): Presence of three copies of a particular chromosome instead of two.
        • Most autosomal trisomies are lethal (e.g., Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13) are significant chromosomal disorders characterized by developmental challenges and distinct physical features.).
        • Some sex chromosome trisomies, such as Klinefelter syndrome (47, XXY), and conditions like triple X syndrome (super female) and XYY syndrome (super male), often result in individuals who can lead relatively normal lives despite certain health risks..
      • II- Monosomy (2n-1): Loss of a single chromosome.
        • Most autosomal monosomies are incompatible with life.
        • Sex chromosome monosomies can sometimes be viable (e.g., Turner syndrome)

    • B- Polyploidy: Presence of three or more sets of chromosomes.

      • Triploidy (3n).
      • Tetraploidy (4n).
      • Pentaploidy (5n).
      • Polyploidy in general.

    Causes of Aneuploidy

    • Nondisjunction: Failure of homologous chromosomes or sister chromatids to separate properly during cell division (meiosis or mitosis).
      • Primary nondisjunction: Failure in the first meiotic division.
      • Secondary nondisjunction: Failure in the second meiotic division or during mitosis.
      • Mosaicisms: Non-disjunction during mitosis, after multiple normal mitotic divisions.
    • Failure of chromosome duplication (during S phase).
    • Anaphase lag (failure of chromosome to move to a pole during anaphase).

    Structural Aberrations

    • Deletion (del): Loss of a portion of a chromosome.
      • Terminal deletion: Loss of the end of a chromosome segment.
      • Interstitial deletion: Loss of an interior segment of a chromosome.
    • Ring chromosome: Two breaks at the ends of a chromosome, with the lost ends joining to form a ring.
    • Inversion: Reversal of a segment of a chromosome.
      • Paracentric: Inversion does not include the centromere.
      • Pericentric: Inversion includes the centromere.
    • Translocation: Transfer of a chromosome segment to a different non-homologous chromosome.
      • Reciprocal translocation: Exchange of segments between two non-homologous chromosomes. (e.g., Philadelphia chromosome).
      • Robertsonian translocation: Fusion of two acrocentric chromosomes at their centromeres, resulting in a single large chromosome and one small chromosome (lost).
    • Insertion: Movement of a part of one chromosome to another (inter- or intra-chromosomal).
    • Isochromosome: Chromosome with mirror image arms (duplication of one arm and deletion of the other).

    Chromosomal Aberration Diagnosis

    • Prenatal screening: Blood tests, ultrasound (e.g., Down syndrome signs).
    • Prenatal tests during pregnancy: Amniocentesis, chorionic villus sampling, percutaneous umbilical blood sampling (cordocentesis).
    • Postnatal diagnosis: Physical examination, karyotyping (analysis of chromosomes), FISH (fluorescence in situ hybridization), banding techniques.

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    Chromosomal Abnormalities Tutorial Session 2024/2025 (PDF)

    Description

    This quiz covers the definitions and types of chromosomal aberrations, including both numerical and structural abnormalities. It will also explore various environmental and medical causes that increase the risk of these anomalies. Test your understanding of the factors contributing to chromosomal disorders.

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