第十章染色体畸变 染色体畸变( chromosome aberration)是体细胞或生殖细胞内染 色体发生的异常改变。畸变的类型和可能引起的后果在细胞不同周期 和个体发育不同阶段不尽相同。 染色体畸变可分为数目畸变和结构畸变两大类,其中染色体的数 目畸变又可分为整倍性改变和非整倍性改变两种。结构畸变主要有缺 失、重复、插入、易位和倒位等;当一个个体细胞有两种或两种以上 的不同核型的细胞系时,这个个体就被称为嵌合体;无论数目畸变, 还是结构畸变,其实质是涉及染色体或染色体节段上基因群的增减或 位置的转移,使遗传物质发生了改变,都可以导致染色体异常综合征, 或染色体病。据调查,出生活婴的0.7%和自发流产胎儿的50%以上均 与染色体畸变有关 General Concepts of chromosome aberration abnormalities of chromosomes may be either numerical or structural and may involve one or more autosomes, sex chromosomes, or both simultaneously. By far the most common type of clinically significant chromosome abnormality is aneup loidy, an abnormal chromosome number due to an extra or missing chromosome, which is alway associated with physical or mental maldevelopment, or both. Reciprocal translocations (exchange of segments between nonhomologous hromosomes )are also relatively common but usually have no phenotypic effect, although as explained later there may be an associated increased risk ofabnormal offspring 第一节染色体畸变发生的原因1 第十章 染色体畸变 染色体畸变（chromosome aberration）是体细胞或生殖细胞内染 色体发生的异常改变。畸变的类型和可能引起的后果在细胞不同周期 和个体发育不同阶段不尽相同。 染色体畸变可分为数目畸变和结构畸变两大类，其中染色体的数 目畸变又可分为整倍性改变和非整倍性改变两种。结构畸变主要有缺 失、重复、插入、易位和倒位等；当一个个体细胞有两种或两种以上 的不同核型的细胞系时，这个个体就被称为嵌合体；无论数目畸变， 还是结构畸变，其实质是涉及染色体或染色体节段上基因群的增减或 位置的转移，使遗传物质发生了改变，都可以导致染色体异常综合征， 或染色体病。据调查，出生活婴的 0.7%和自发流产胎儿的 50%以上均 与染色体畸变有关。 General Concepts of Chromosome Aberration Abnormalities of chromosomes may be either numerical or structural and may involve one or more autosomes, sex chromosomes, or both simultaneously. By far the most common type of clinically significant chromosome abnormality is aneuploidy, an abnormal chromosome number due to an extra or missing chromosome, which is always associated with physical or mental maldevelopment, or both. Reciprocal translocations (exchange of segments between nonhomologous chromosomes) are also relatively common but usually have no phenotypic effect, although as explained later there may be an associated increased risk of abnormal offspring. 第一节 染色体畸变发生的原因