Tools for the Gene Technologist | 基因技术工具

📚 Tools for the Gene Technologist | 基因技术工具

A gene technologist relies on a toolkit of enzymes, vectors and laboratory techniques to isolate, modify, amplify and analyse DNA. This article summarises the essential tools used in A-level Cambridge Biology, from restriction enzymes to CRISPR-Cas9, and explains how each contributes to genetic engineering, diagnosis and research.

基因技术人员依靠一系列酶、载体和实验技术来分离、修饰、扩增和分析DNA。本文总结了A-level剑桥生物课程中使用的核心工具，从限制酶到CRISPR-Cas9，并解释每种工具如何为基因工程、诊断和研究做出贡献。

1. Restriction Endonucleases | 限制性内切酶

Restriction endonucleases are enzymes, originally isolated from bacteria, that cut DNA molecules at specific base sequences called recognition sites. Most recognition sites are 4-8 base pairs long and are often palindromic, meaning the sequence reads the same on both strands in the 5′ to 3′ direction.

限制性内切酶是最初从细菌中分离出来的酶，可以在称为识别位点的特定碱基序列处切割DNA分子。大多数识别位点长4-8个碱基对，通常具有回文结构，即两条链从5’到3’方向读取的序列相同。

Some restriction enzymes make staggered cuts that leave single-stranded overhangs called sticky ends; others cut both strands at the same position to produce blunt ends. Sticky ends are especially useful because complementary overhangs from different DNA molecules can base-pair before ligation.

一些限制酶产生交错切口，留下称为黏性末端的单链突出端；另一些限制酶在同一位置切割两条链，产生平末端。黏性末端特别有用，因为来自不同DNA分子的互补突出端可以在连接前进行碱基配对。

EcoRI: 5′-G↓AATTC-3′ generates sticky end AATT

2. DNA Ligase | DNA 连接酶

DNA ligase catalyses the formation of phosphodiester bonds between adjacent nucleotides, sealing breaks in the sugar-phosphate backbone of DNA. In genetic engineering, it is used after restriction digestion to join the sticky ends of a vector and a donor DNA fragment.

DNA连接酶催化相邻核苷酸之间形成磷酸二酯键，从而封闭DNA糖-磷酸骨架中的缺口。在基因工程中，它被用于在限制酶消化后连接载体和供体DNA片段的黏性末端。

The enzyme requires ATP as an energy source. First, hydrogen bonds hold complementary sticky ends together; ligase then creates covalent bonds, producing a stable recombinant DNA molecule.

该酶需要ATP作为能量来源。首先，氢键将互补的黏性末端固定在一起；然后连接酶形成共价键，产生稳定的重组DNA分子。

3. Plasmids as Cloning Vectors | 质粒作为克隆载体

Plasmids are small, circular, double-stranded DNA molecules found naturally in bacteria. They replicate independently of the bacterial chromosome and can be engineered to carry foreign DNA into host cells, acting as cloning vectors.

质粒是天然存在于细菌中的小型环状双链DNA分子。它们独立于细菌染色体进行复制，可被改造为携带外源DNA进入宿主细胞的载体，即克隆载体。

A useful plasmid vector contains an origin of replication, a multiple cloning site with several unique restriction enzyme sequences, and selectable marker genes such as antibiotic resistance. The same restriction enzyme is used to cut both the plasmid and

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