8 Chromosome Disorder
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8 Chromosome Disorder

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8 Chromosome Disorder 8 Chromosome Disorder Presentation Transcript

  • Chromosome disorders Weiying Jiang Department of Medical Genetics P33
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  • Human chromosome
  • What is chromosome? Chromosomes are complex structures located in the cell nucleus, they are composed of DNA, histone and non-histone proteins, RNA , and polysaccharides. They are basically the "packages" that contain the DNA.
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  • A group——1 ~ 3 B group——4 ~ 5 C group——6 ~ 12 +X D group——13 ~ 15 E group——16 ~ 18 F group——19 ~ 20 G group——21 ~ 22 +Y Classification
  • Metacentric (Chromosome 1) Submetacentric (Chromosome 9) Acrocentric (Chromosome 14)
  • Methods of chromosome analysis Karyotype analysis
  • Methods of chromosome analysis Karyotype analysis (G banding )
  • Methods of chromosome analysis Fluoresent in-situ hybridization (FISH) Utilizing fluorescently labeled DNA probes to detect or confirm gene or chromosome abnormalities that are generally beyond the resolution of routine Cytogenetics
  • Metaphase FISH
  • Interphase FISH FISH can be used in interphase cells to determine the chromosome number of one or more chromosomes as well as to detect some specific chromosome rearrangements that are characteristic for certain cancers. The primary advantage of interphase FISH is that it can be performed very rapidly if necessary, usually within 24 hours, because cell growth is not required.
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  • Comparative Genomic Hybridization ( CGH ) ATCGGATCATGCGTA TAGCCTAGTACGCAT
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  • Disadvantages : Resolution Technical difficulties 10 mega-bases for losses 2 mega-bases for gains Providing the start point for position cloning, but the precise localization
  • Array CGH
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  • Advantages : Resolution 30,000 overlapping mapped clones (one clone per mega-base) Oligonucleotide array includes up 500,000 probes
  • Chromosome abnormality Numerical abnormality Structural abnormality Aneuploidy Polyploidy translocation deletion insertion inversion rings isochromosome
  • Numerical abnormality 46 chromosomes 23 chromosomes = one set of chromosomes
  • Diploidy
  • Aneuploidy: One or a few chromosomes ,except 23 ones , above or below the normal chromosome number. For example, three number 21 chromosomes or trisomy 21.
  • The common aneuploidy: Patau syndrome: (trisomy 13) Edwards syndrome: (trisomy 18) Down’s syndrome: (trisomy 21)
  • The common aneuploidy: Turner’s syndrome: (45, X)
  • Normal XX X X l l l l
  • Non-disjunction In meiosis
  • Non-disjunction During Mitosis Mosaicism
  • Polyploidy More than two sets of chromosomes per nucleus. 23 chromosomes = one set of chromosomes 69,XXY 92,XXXY
  • Diandry Digyny
  • Structure of chromosome abnormality
  • 46,XY,t(5;8)(q31.1;p23).
  • A C B D Synapsis
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  • Robertsonian Translocation
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  • 46,XX,del(16)(q13q22
  • 46,XY,inv(10)(q11.23q26.3) . Inversion
  • A C B D Synapsis
  • Pericentric inversion Paracentric inversion 1 2 3 4 1 4 2 3 1 2 4 3
  • 46,XY,+13,dic(13;14)(p11.2;p11.2) .
  • Ring chromosome
  • Chromosome abnormality Numerical abnormality Structural abnormality Aneuploidy Polyploidy translocation deletion insertion inversion rings isochromosome
  • Thank you !