Chromosomal Abnormalities Lecture
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Questions and Answers

What is the main cause of structural chromosomal abnormalities?

  • Maternal age
  • Genetic mutations
  • Viral infections (correct)
  • Ionizing radiation (correct)

    • What is the result of unbalanced chromosomal rearrangement?

  • No effect on the individual
  • Severe clinical effects (correct)
  • Only affects the mother
  • Harmless effects

    • What is the characteristic of balanced chromosomal rearrangement?

  • It results in severe clinical effects
  • It is only seen in maternal chromosomes
  • It is usually harmless (correct)
  • It only affects the father

    • What is the result of deletion of a short arm of chromosome 5?

    <p>Cri-du-Chat syndrome</p> Signup and view all the answers

    What is the technique used to detect micro-deletion?

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

    What is the condition characterized by underdevelopment of the larynx and a characteristic cat-like cry?

    <p>Cri-du-Chat syndrome</p> Signup and view all the answers

    What is the type of inversion that involves both p and q arms?

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

    What is the indication for routine chromosome investigation?

    <p>All of the above</p> Signup and view all the answers

    What is the result of terminal deletion of a chromosome?

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

    What is the type of structural chromosomal abnormality that results in extra copies of a chromosome part?

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

    What is the result of a paracentric inversion?

    <p>A segment of one arm is involved and inverted.</p> Signup and view all the answers

    What is the characteristic of a ring chromosome?

    <p>Loss of telomeres or ends of both arms of a chromosome.</p> Signup and view all the answers

    What is the result of an isochromosome?

    <p>Creation of two non-identical chromosomes.</p> Signup and view all the answers

    What is the result of an insertion?

    <p>Rearrangement of genetic material to a non-homologous chromosome.</p> Signup and view all the answers

    What is the characteristic of a reciprocal translocation?

    <p>Rearrangement of genetic material between two non-homologous chromosomes.</p> Signup and view all the answers

    What is the result of a Robertsonian translocation?

    <p>Rearrangement of genetic material between two acrocentric chromosomes.</p> Signup and view all the answers

    What is the notation for a normal female karyotype?

    <p>46,XX</p> Signup and view all the answers

    What is the notation for a deletion of a segment on the short arm of chromosome 5?

    <p>46,X,5p-</p> Signup and view all the answers

    What is the characteristic of balanced structural abnormalities?

    <p>May result in a loss or gain of genetic material.</p> Signup and view all the answers

    What is the characteristic of unbalanced structural abnormalities?

    <p>Always result in a loss of genetic material.</p> Signup and view all the answers

    Study Notes

    Chromosomal Abnormalities

    • Chromosomal abnormalities result from breakage and incorrect rejoining of chromosomal segments, leading to disease.
    • Environmental factors responsible for structural abnormalities include: • Ionizing radiation • Ultraviolet light • Chemical agents • Viral infections

    Indications for Chromosome Investigation

    • Prenatal screening: • Down's syndrome, especially in cases of advanced maternal age (>35 years) or family history of chromosome abnormality • Abnormal ultrasound scan of fetus
    • Birth defects: • Malformations • Mental retardation
    • Abnormal sexual development (e.g., Klinefelter's syndrome)
    • Infertility
    • Recurrent fetal loss

    Types of Structural Chromosomal Abnormalities

    • Balanced rearrangements: • Exchange or rearrangement of genetic material without loss or gain of genetic material • Generally harmless, but carriers are at risk of producing children with unbalanced chromosomal complement
    • Unbalanced rearrangements: • Incorrect amount of chromosomal material, resulting in severe clinical effects

    Deletions

    • Loss of genetic material, resulting in monosomy for the segment of the chromosome
    • Types of deletions: • Terminal deletion: involves a single break of the terminal part of the chromosome • Interstitial deletion: involves two breaks and loss of the intervening portion of the chromosome
    • Example: Cri-du-Chat syndrome (46,XX,5p- or 46,XY,5p-)

    Duplications

    • Extra copies of a chromosome part

    Inversions

    • Involves two breaks along the chromosome, resulting in a reversal of a segment
    • Types of inversions: • Pericentric inversion: involves both p and q arms with centromere • Paracentric inversion: involves only one arm

    Ring Chromosomes

    • Loss of telomeres or ends of both arms of a chromosome, forming a ring structure

    Isochromosomes

    • Creation of two non-identical chromosomes, one with a combination of short arms, the other with a combination of long arms

    Insertions

    • Rearrangement of genetic material to a non-homologous chromosome, without loss of genetic material

    Translocations

    • Exchange of genetic material between two chromosomes
    • Types of translocations: • Reciprocal translocation: no loss of genetic material, but an exchange of genetic material between two non-homologous chromosomes • Robertsonian translocation (centric fusion): involves break at or near the centromere in two acrocentric chromosomes and subsequent fusion of their long arms

    Karyotype Nomenclature

    • Normal female or male: 46,XX or 46,XY
    • Extra or missing entire chromosome: e.g., 47,XX,+21 or 45,XX,-15
    • Missing piece of a chromosome: e.g., 5p-
    • Other notations include: • del (deletion) • dup (duplication) • inv (inversion) • ins (insertion) • rob (Robertsonian translocation) • t (translocation)

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    Description

    A lecture on chromosomal abnormalities, specifically structural abnormalities, covering topics such as breakage and reunion events. Presented by Dr. Dhamyaa K. Kadhim.

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