基因突变是指基因内部的化学变化,其实质是有遗传效应的 DNA 片段内核苷酸序列的改变。突变的最小单位是单个核苷酸。一般由于基因很小,单个核苷酸更小,基因突变在光镜和电镜下都无法直接看到,只能根据突变对表现型最显著的效应来鉴定。据此,可把突变概分为:(1)可见突变,即在生物体的表现型中看得到的突变效应;(2)生化突变,会 Gene mutation refers to the chemical changes within the gene, which is essentially the genetic effect of DNA fragments within the nucleotide sequence changes. The smallest unit of mutation is a single nucleotide. Generally, genes are small and single nucleotides are smaller. Mutations can not be seen directly under light and electron microscopes. They can only be identified based on the phenotypic effects of mutations on phenotypes. Accordingly, the mutation can be summarized as: (1) a visible mutation, ie, a mutational effect that can be seen in the organism’s phenotype; (2) a biochemical mutation that