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Biology LibreTexts

9.S: Changes in Chromosome Number and Structure (Summary)

  • Page ID
    4127
  • [ "article:topic", "authorname:tnickle" ]

    • Errors during anaphase in mitosis or meiosis can lead to trisomy and other forms of aneuploidy.
    • Errors during the repair of DNA breaks or during meiotic crossing over can lead to chromosome rearrangements.
    • Five common forms of aneuploidy in humans are 47,sex,+21 (Down syndrome),  47,XYY,  47,XXX,  45,X (Turner syndrome) and  47,XXY (Klinefelter syndrome).
    • Deletion(5) causes a serious condition (cri-du-chat syndrome) because deletions are unbalanced chromosome rearrangements.
    • Inversion(9) causes few health consequences because inversions are balanced chromosome rearrangements.
    • Bright field microscopy can be used to detect chromosome number abnormalities and some chromosome rearrangements.
    • Fluorescence in situ hybridization can be used to detect all types of chromosome abnormalities.
    • PCR and DNA chip based techniques can be used to detect chromosome number abnormalities, deletions, and duplications.

    Key Terms:

    origin of replication

    telomere

    centromere

    non-disjunction

    euploid

    aneuploid

    balanced

    unbalanced

    first division nondisjunction

    second division nondisjunction

    double strand break

    nonhomologous end joining

                    DNA repair system

    chromosome rearrangement

    deletion

    inversion

    paracentric inversion

    pericentric inversion

    tandem duplication

    translocation

    reciprocal translocation

    Robertsonian translocation

    meiotic crossover

    deletion loop

    karyotype

    46,XX

    46,XY

    47,sex,+21 (Down syndrome)

    trisomy

    47,XYY

    47,XXX

    monosomy

    45,X (Turner syndrome)

    pseudoautosomal region

    47,XXY (Klinefelter syndrome)

    46,sex,deletion(5)
              (cri-du-chat syndrome)

    46,sex,inversion(9)

    bright field microscopy

    Giemsa stain

    fluorescence in situ hybridization

    fluorescent probe

    DAPI stain

    amniocentesis

    Contributors