IGCSE Edexcel Biology: Gene Mutations Exam Points | IGCSE Edexcel 生物：基因突变 考点精讲

📚 IGCSE Edexcel Biology: Gene Mutations Exam Points | IGCSE Edexcel 生物：基因突变 考点精讲

Welcome to this focused revision guide on gene mutations for the IGCSE Edexcel Biology specification. Mutations are permanent changes in the DNA base sequence; they can alter the structure and function of proteins, leading to new alleles and contributing to genetic diversity. In this article, you will learn about the different types of mutations, how they affect protein synthesis, what causes them, and their role in evolution – all aligned with Edexcel exam requirements.

欢迎阅读本文精心编写的IGCSE Edexcel生物基因突变考点精讲。突变是DNA碱基序列的永久性改变，它们可能改变蛋白质的结构与功能，从而产生新的等位基因，增加遗传多样性。本文将系统讲解突变的类型、对蛋白质合成的影响、成因以及在进化中的作用，全面贴合Edexcel考纲要求。

1. What Are Mutations? | 什么是基因突变？

A gene mutation is a random and permanent alteration in the nucleotide sequence of DNA. These changes may involve a single base pair or larger segments of a chromosome, but in IGCSE we focus on gene mutations (point mutations and small insertions/deletions).

基因突变是DNA核苷酸序列中随机的、永久性的改变。这些变化可能涉及单个碱基对或染色体较大片段，但IGCSE主要关注基因突变（点突变和小片段插入/缺失）。

Mutations are the ultimate source of new alleles – variants of a gene. Without mutations, all individuals would have identical alleles, and no heritable variation would exist.

突变是产生新等位基因（基因变体）的最终来源。没有突变，所有个体的等位基因完全相同，就不会存在可遗传的变异。

If a mutation occurs in a body cell (somatic), it cannot be passed to offspring. However, if it takes place in a gamete, the altered allele can be inherited, potentially affecting the next generation.

如果突变发生在体细胞中，它不会传递给后代；但如果发生在配子中，改变的等位基因可以遗传，可能影响下一代。

2. Types of Gene Mutations | 基因突变的类型

Gene mutations are broadly divided into substitutions, insertions, and deletions. Substitutions are point mutations where one base is swapped for another. Insertions and deletions (indels) add or remove bases, often causing a frameshift in the genetic code.

基因突变大致分为碱基替换、插入和缺失。替换是点突变，即一个碱基被另一个碱基替换。插入和缺失（indels）会添加或移除碱基，往往导致遗传密码发生移码。

The effect of a mutation depends on where it occurs in the

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