Chromosomal Aberrations and Structure Changes
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Questions and Answers

What is referred to as chromosomal aberration?

  • Alterations in the physical structure or number of chromosomes (correct)
  • Only structural alterations in chromosomes
  • Changes in the genetic information of chromosomes
  • Changes occurring only in chromosome numbers

    • Which of the following is NOT a primary way to alter the structure of chromosomes?

  • Insertions (correct)
  • Inversions
  • Duplications
  • Deletions

    • What can result from structural chromosome rearrangements?

  • Improved genetic diversity
  • Birth defects (correct)
  • Increased fertility
  • Reduction in mutation rates

    • How are chromosomal aberrations classified?

    <p>Into structural and numerical variations</p> Signup and view all the answers

    What happens during duplication in chromosome alteration?

    <p>Extra copies of a segment are formed</p> Signup and view all the answers

    What is an example of a chromosomal mutation?

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

    Which type of chromosomal alteration does not change the amount of genetic information?

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

    Which of the following best describes translocation in chromosome structure alteration?

    <p>Swapping segments between non-homologous chromosomes</p> Signup and view all the answers

    Which condition can result from structural chromosome rearrangements?

    <p>Mental retardation</p> Signup and view all the answers

    What type of chromosome alteration increases the total amount of genetic information?

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

    What is a result of a deletion in a homozygous wild-type organism?

    <p>It can give a normal phenotype.</p> Signup and view all the answers

    What typically causes chromosome breakage leading to deletions?

    <p>Exposure to radiation or chemicals.</p> Signup and view all the answers

    What is meant by an 'interstitial deletion'?

    <p>Two breaks occur in a middle portion of the chromosome.</p> Signup and view all the answers

    What is a consequence of deletion of the centromere in a chromosome?

    <p>It leads to an acentric chromosome that is usually lost.</p> Signup and view all the answers

    What happens during the process of duplication in chromosomes?

    <p>A chromosomal fragment is added, increasing gene count.</p> Signup and view all the answers

    How do duplications typically arise in chromosomes?

    <p>Due to unequal crossing over during meiosis.</p> Signup and view all the answers

    Which of the following disorders is associated with large chromosomal deletions?

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

    What is a common outcome of duplications in chromosomes compared to deletions?

    <p>Duplications do not produce drastic consequences in terms of phenotype.</p> Signup and view all the answers

    What effect does the Bar allele have on Drosophila eye shape?

    <p>It reduces the number of eye facets.</p> Signup and view all the answers

    What occurs during prophase I in relation to duplication loops?

    <p>Loops form maximizing pairing of related regions.</p> Signup and view all the answers

    What is the consequence of inversion in homozygotes during meiosis?

    <p>Meiosis proceeds normally.</p> Signup and view all the answers

    What is an inversion loop's purpose in heterozygotes?

    <p>To maximize the alignment of homologous regions.</p> Signup and view all the answers

    How are gametes affected by pericentric and paracentric inversions?

    <p>Gametes produced are imbalanced.</p> Signup and view all the answers

    What distinguishes a reciprocal translocation from a simple translocation?

    <p>Reciprocal translocation involves breakage in two non-homologous chromosomes.</p> Signup and view all the answers

    What is a simple translocation?

    <p>The attachment of a segment to a non-homologous chromosome.</p> Signup and view all the answers

    What may occur as a result of crossing-over in a heterozygous inversion?

    <p>It can produce serious genetic consequences.</p> Signup and view all the answers

    Study Notes

    Introduction

    • Structural chromosome rearrangements are changes in the physical structure of chromosomes.
    • These changes may result in birth defects, mental retardation, increased risk for infertility.
    • Chromosomal aberrations are substantial changes in chromosome structure.
      • They typically affect more than one gene.
      • They are also called chromosomal mutations.

    Alterations in Chromosome Structure

    • Duplication
      • The total amount of genetic information in the chromosome can change.
      • A chromosomal fragment is attached to a chromosome, adding one or more genes.
    • Deletions
      • The total amount of genetic information in the chromosome can change.
      • A portion of a chromosome is deleted.
    • Inversion
      • The genetic material may remain the same but rearranged.
      • A segment of a chromosome rotates 180 degrees.
    • Translocation
      • The genetic material may remain the same but rearranged.
      • A segment of chromosome integrates into a non-homologous chromosome.

    Deletion

    • Loss of genetic material
      • A deficiency is a loss of one or more genes.
      • Can be terminal (end of chromosome) or interstitial (middle of chromosome).
    • Causes
      • Caused by various agents such as radiation, chemicals, drugs, or viruses.
    • Consequences
      • Deletion of the centromere results in an acentric chromosome that is lost, usually with serious or lethal consequences.
    • Examples of human disorders caused by large chromosomal deletions:
      • Cri-du-chat (“cry of the cat”) syndrome, resulting from deletion of part of the short arm of chromosome 5.
      • The deletion results in severe mental retardation and physical abnormalities.

    Duplication

    • Gain of genetic material
      • A duplication involves attachment of a chromosomal fragment resulting in addition of one or more genes to a chromosome.
    • Origin
      • Unequal crossing over during meiosis:
        • Homologous chromosomes are paired in a perfect manner so that identical loci lie exactly opposite each other.
        • If paired chromosomes are misaligned, equal exchange products are not formed resulting in duplications.
    • Consequences
      • Do not produce any drastic consequences as like deletion in terms of phenotype and survival.

    Inversion

    • Reversal of chromosome segment
      • A chromosome segment excises and reintegrates oriented 180° from the original orientation.
      • Pericentric inversion: includes the centromere.
      • Paracentric inversion: does not include the centromere.
    • Consequences
      • Linked genes are often inverted together.
      • Meiotic consequences depend on the inversion occurring in a homozygote or heterozygote.
        • Homozygote will have normal meiosis.
        • Heterozygote may produce unequal crossover products with serious consequences.

    Translocation

    • Transfer of chromosome segment
      • Integration of chromosome segment into a non-homologous chromosome.
      • Simple Translocation: A small terminal segment of a chromosome attaches to the end of a homologous chromosome or to a non-homologous chromosome.
      • Reciprocal Translocation: The breakage takes place in two non-homologous chromosomes and is followed by the reunion of broken segments to different chromosomes.

    History

    • 1923: C.B. Bridges discovered duplications, deletions, and translocations in chromosomes.
    • 1926: A.H. Sturtevant discovered inversions in chromosomes.

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    Chromosomal Aberrations PDF

    Description

    Explore the fascinating world of structural chromosome rearrangements in this quiz. Discover the implications of chromosomal aberrations such as duplications, deletions, inversions, and translocations, and their effects on genetic information. Test your knowledge on how these changes can impact health and fertility.

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