《医学遗传学》7年制课件Chromosomal Aberration.ppt

5．Chromosomal Aberration 5.2．Structural Aberration 5.2.4. Ring Chromosome (r) A ring chromosome is a chromosome that is formed when the ends have been lost, and the arms fuse together to form a ring. Ring Chromosome 2p21 2q31 Ring Chromosome 2p21 2q31 5．Chromosomal Aberration 5.2．Structural Aberration 5.2.5. Isochromosome (i) An isochromosome is a chromosome that has lost one of its arms and replaced it with an exact copy of the other arm. Isochromosome Isochromosome Isochromosome Meiotic Non-Disjunction 2N N N+1 N-1 2N+1 2N+1 2N-1 2N-1 N+1 N+1 N-1 N-1 2N 2N 2N+1 2N-1 2N N N N N N-1 N+1 Meiotic Non-Disjunction Primary non-disjunction Trisomy offspring arise from chromosome non-disjunction at meiosis of previously normal parent. Meiotic Non-Disjunction Secondary non-disjunction Trisomy offspring arise from segregation at meiosis of an already-trisomy parent. Meiotic Non-Disjunction 2N+1 N 2N 2N 2N+1 2N+1 N N+1 N N N+1 N+1 Secondary non-disjunction Mitotic Non-Disjunction Mitotic non-disjunction arises from failure of sister chromatids to disjoin at mitotic anaphase. Mitotic Non-Disjunction Mosaic A mosaic denotes the presence of two or more populations of cells with different karyotypes in one individual. Mitotic Non-Disjunction 2N 2N-1 2N+1 47/45 Mosaic 2N 2N 2N 2N 2N 2N-1 2N+1 46/47/45 Mosaic Mosaic 5．Chromosomal Aberration 5.1．Numerical Abnormality 5.1.2. Aneuploid Mechanism of Aneuploid Chromosome non-disjunction Chromosome loss Chromosome Loss The causality where a chromosome is missing from the new cell created via cell division. Anaphase lag may be due to delayed movement of a chromosome at anaphase. 5．Chromosomal Aberration 5.2．Structural Aberration The Breakage and the Rejoin after breakage are the basis of chromosomal structural aberration. Chromosomal rearrangement Rearrangement chromosome 5．Chromosomal Aberration 5.2．Structural Aberration The Breakage and the Rejoin after breakage are the basis of chromosomal structural aberration. Short system Detail