染色体畸变结构改变.pptxVIP

Chromosomal Abnormalities (染色体畸变);Cytogenetics (细胞遗传学) is the field of study involving examination of the genetic material of the cells. The genetic material (DNA) is contained in chromosomes. Each organism has a characteristic number and arrangement of chromosomes.;A karyotype （核型） is a photograph of the chromosomes at metaphase, when they are most easily seen. In a karyotype, the chromosomes are arranged by pairs: alterations in chromosome size (structure) or number are seen here.;Normal Human Karyotype;Chromosomal Abnormalities;Common Structural Abnormalities;Common Structural Abnormalities;(一) Deletions ; 牛牛文库文档分享;(1)无着丝粒断片：最初发生缺失的细胞在分裂时可见落后染色体——无着丝粒断片， (2)顶端缺失 有丝分裂出现因断裂—融合→双着丝粒染色体——后期染色体桥。 减数分裂联会时，有未配对的游离区段。 (3)中间缺失 减数分裂染色体联会时形成缺失环。 注意：较小的缺失往往并不表现出明显的细胞学特征；缺失纯合体减数分裂过程也无明显的细胞学特征。;缺失的细胞学特征;断裂(breakage)—融合(fusion)—桥(bridge);玉米缺失杂合体粗线期缺失环;果蝇唾腺染色体的缺失环;(1)缺失的后果 打破了基因的连锁平衡，破坏了基因间的互作关系，基因所控制的生物功能或性状可能丧失或异常。 (2)缺失的危害程度 取决于缺失区段的大小、缺失区段所含基因的多少、缺失基因的重要程度、染色体倍性水平。 缺失纯合体——致死或半致死 缺失杂合体——缺失区段较长时，生活力差、配子(尤其是花粉)败育或育性降低；缺失区段较小时，可能会造成假显性现象或其它异常现象(猫叫综合症)。;缺失杂合体的假显性现象;Micro Deletions（教材下册p8 ）;1 in 50000 newborns; 牛牛文库文档分享; 牛牛文库文档分享;Cri du chat syndrome ;(二)Duplication的细胞学特征; 重复的遗传学效应;果蝇复眼的小眼组成数目的剂量效应;（三）Inversion; 牛牛文库文档分享;Inversion Loop;Inversion Loop （倒位环）;Paracentric Inversion Crossover ;Pericentric Inversion Crossover ;Dicentric Chromosomes are Unstable; 倒位的细胞学鉴定; 倒位的遗传效应; 倒位的遗传效应;(四)Translocation;When a part of one chromosome is relocated to another chromosome, the result is called a translocation If parts of two chromosomes “trade places” so no genetic material is lost, it is called a reciprocal (or balanced) translocation; 相互易位的细胞学鉴定;Balanced Translocations Pair “Oddly” during Meiosis;Depending on the segregation pattern in a single meiotic division, all of the gametes may have normal DNA content (but half have the translocation), or all of the gametes may be defective (have duplication and deletion);易位杂合体的联会和分离;果蝇巨染色体易位图;易位的遗传学效应;1960年，Nowell ——慢性粒细胞白血病(C