第三章基因突变 一切生物细胞内的基因都能保持其相对稳定性,但在一定内外因 素的影响下,遗传物质就可能发生变化,这种遗传物质的变化及其所 引起的表型改变称为突变( mutation)。广义的突变包括染色体畸变 ( chromosome aberration)和基因突变( gene mutation)。前者将在以 后章节中介绍,本章着重讨论基因突变,它主要指基因组DNA分子 在结构上发生碱基对组成或序列的改变,它通常只涉及到某一基因的 部分变化。基因突变是生物界中所存在的普遍现象,也是生物进化发 展的根本源泉 基因突变可发生在生殖细胞,也可发生在体细胞,后者称为体细 胞突变( somatic mutation)。生殖细胞中的突变基因可通过有性生殖遗 传给后代,并存在于子代的每个细胞里,从而使后代的遗传性状发生 相应改变。体细胞突变则不会传递给子代,但可传递给由突变细胞分 裂所形成的各代子细胞,在局部形成突变细胞群而成为病变甚至癌变 的基础。 Mutation Mutations can occur in any cells, both in germline cells and in somatic cells. Only germline mutations, however, can be perpetuated from one generation to the next and are thus the ones responsible for inher ited disease. This is not to say, however, that somatic cell mutations are not medically important. Indeed, the vast majority of cell divisions that produce an adult organism of an estimated 10 3 cells from a single-cell zy gote occur in somatic lineages, and thus most mutations occur there Somatic mutations in a number of genes can give rise to a significant proportion of cancers, as a result of any of the three types of mutation (genome mutation, chromosome mutation and gene mutation ). In this sense, cancer is fundamentally a genetic" disease, and mutations are central to its etiology or progression. Moreover, somatic mutation at the level of the genome, the chromosome, or the gene, which result in somatic mosaicism, is well-documented cause of phenotypic variation.第三章 基因突变 一切生物细胞内的基因都能保持其相对稳定性，但在一定内外因 素的影响下，遗传物质就可能发生变化，这种遗传物质的变化及其所 引起的表型改变称为突变（mutation）。广义的突变包括染色体畸变 （chromosome aberration）和基因突变（gene mutation）。前者将在以 后章节中介绍，本章着重讨论基因突变，它主要指基因组 DNA 分子 在结构上发生碱基对组成或序列的改变，它通常只涉及到某一基因的 部分变化。基因突变是生物界中所存在的普遍现象，也是生物进化发 展的根本源泉。 基因突变可发生在生殖细胞，也可发生在体细胞，后者称为体细 胞突变（somatic mutation）。生殖细胞中的突变基因可通过有性生殖遗 传给后代，并存在于子代的每个细胞里，从而使后代的遗传性状发生 相应改变。体细胞突变则不会传递给子代，但可传递给由突变细胞分 裂所形成的各代子细胞，在局部形成突变细胞群而成为病变甚至癌变 的基础。 Mutation Mutations can occur in any cells, both in germline cells and in somatic cells. Only germline mutations, however, can be perpetuated from one generation to the next and are thus the ones responsible for inherited disease. This is not to say, however, that somatic cell mutations are not medically important. Indeed, the vast majority of cell divisions that produce an adult organism of an estimated 1013 cells from a single-cell zygote occur in somatic lineages, and thus most mutations occur there. Somatic mutations in a number of genes can give rise to a significant proportion of cancers, as a result of any of the three types of mutation (genome mutation, chromosome mutation and gene mutation). In this sense, cancer is fundamentally a “genetic” disease, and mutations are central to its etiology or progression. Moreover, somatic mutation at the level of the genome, the chromosome, or the gene, which result in somatic mosaicism, is well-documented cause of phenotypic variation