10.S: Changes in Chromosome Number and Structure (Summary)
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- Ying Liu
- City College of San Francisco
- 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:
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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 |