Name: dna structure and base pairing
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 1 min 16 s
Channel: JoVE

K12 Standards

Minnesota Academic Standards in Science

9-12

Life Science

1.1.1 9L.1.1.1.1

The DNA Helix

脱氧核糖核酸或DNA 由两条多核苷酸链组成。
 每一个由四种类型的核苷酸亚基组成， 其由单个磷酸基团和附着于 糖脱氧核糖的含氮碱基，腺嘌呤，A，胞嘧啶，C， 鸟嘌呤，G或胸腺嘧啶T组成。
 这种排列产生了DNA结构的 糖-磷酸骨架。
 在三个末端的一条链上， 糖被取向，其中羟基暴露 在第三个碳原子上，其准备通过磷酸二酯键 共价连接到第五个碳原子链中 的另一个糖分子。
 在相对的反平行链中， 每个碱基是唯一配对的，C与G和A与T， 这是由于它们之间形成的 氢键数量的差异。
 这个互补的一面终止于五个 主要末端的磷酸基团。
 这种化学极性确保有效填充， 将两股线彼此缠绕以形成3-D双螺旋， 每个整圈具有10个碱基对。

祈祷，莱斯利。"DNA 结构和功能的发现:Watson 和 Crick。"自然教育 1，第 1 期（2008 年）:100。[<a href="https://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397">来源</a>]

dna双螺旋

“脱氧核糖核酸（脱氧核糖核酸，简称DNA）是一种遗传物质，负责在所有生物体和大多数病毒中一代又一代地传递性状。DNA是由两股核苷酸组成的，它们缠绕在一起形成双螺旋。DNA结构的发现在近一个多世纪中逐渐出现，代表了科学史上最著名、最迷人的故事之一。”

<h4>DNA结构细节</h4>
 
每一条DNA链都包含称为核苷酸的亚单位，核苷酸含有糖脱氧核糖、磷酸基和四种含氮碱基之一：腺嘌呤（A）、鸟嘌呤（G）、胞嘧啶（C）和胸腺嘧啶（T）。腺嘌呤和鸟嘌呤是一类称为嘌呤的化学物质，它们都含有两个环状结构。胞嘧啶和胸腺嘧啶属于一类称为嘧啶的单环结构。
 
同一链中的相邻核苷酸通过磷酸二酯键共价连接。两股核苷酸通过氢键连接在一起，其中一股腺嘌呤与另一股胸腺嘧啶位于同一位置，另一股腺嘌呤与鸟嘌呤位于同一位置。这种氢键是通过两条DNA链的反平行排列实现的，在这种排列中，两条DNA链的5端和3端方向相反。如果没有这种排列，核苷酸将处于错误的位置，在链之间形成氢键。
 
DNA分子的两股紧密缠绕成弹簧状结构，称为双螺旋。然而，双螺旋并不是完全对称的。相反，结构中有规律地出现凹槽。主要的凹槽发生在糖磷酸主干相对较远的地方。这个空间允许获得DNA结合蛋白，如转录因子。相比之下，凹槽则发生在磷酸糖主干紧密相连的地方。相对较少的蛋白质通过凹槽与DNA结合。
 
<h4>DNA 结构的发现：简史</h4>
 
DNA结构的发现始于1869年，当时瑞士科学家弗雷德里希·米歇尔（Friedrich Miescher）发现了一种他称为“核酸”的物质。在从白细胞中提取蛋白质的过程中，米歇尔发现了一种意想不到的物质，磷含量相对较高。他不知道它是什么，但他怀疑它可能在生物学上很重要。 米歇尔是对的，但是科学界花了几十年的时间才完全理解他的见解。
 
下一个重要发现是由俄罗斯生物化学家菲巴斯·利文（Phoebus Levene）发现的。1919年，利文提出，当时称为核酸的核酸是由分子链组成的，他称之为多核苷酸。利文的提议源于他对酵母的研究，在研究中他发现单个核苷酸由磷酸基、糖和含氮基组成。尽管利文的多核苷酸模型在许多方面是正确的，但仍不清楚碱基在DNA分子中是如何排列的。
 
奥地利生物化学家埃尔文·查戈夫（Erwin Chargaff）扩展了利文的工作。在20世纪40年代末的研究中，查戈夫发现了一个重大发现：DNA中腺嘌呤的含量总是大致等于胸腺嘧啶的含量，鸟嘌呤的含量总是大致等于胞嘧啶的含量。这种模式被称为查戈夫规则，是最终解释DNA结构的关键证据。
 
20世纪50年代初，美国生物学家詹姆斯·沃森（James Watson）和英国物理学家弗朗西斯·克里克（Francis Crick）正与他们的主要竞争对手美国的莱纳斯·鲍林（Linus Pauling）竞争，以发现DNA的三维结构。在查戈夫工作的基础上，他们利用物理、数学和化学知识构建了DNA的物理模型。但他们没有成功，直到他们收到一个关键的数据：一张DNA的X光照片，精确地显示了它的双螺旋结构。这张照片是物理学家罗莎琳德·富兰克林（Rosalind Franklin）未发表的数据，在富兰克林不知情的情况下，交给了沃森和克里克。沃森和克里克，与莫里斯•威尔金斯（Maurice Wilkins，富兰克林的同事)一起在1953年发表了他们对DNA结构的描述，因这一发现获得了1962年诺贝尔生理学或医学奖。不幸的是，富兰克林于1958年去世，因此没有资格获得诺贝尔奖。

DNA双螺旋

概述

脱氧核糖核酸（DNA）是所有生物体及大多数病毒中负责将遗传性状代代传递的遗传物质。

Education

教育

JoVE Core

Molecular Biology

分子生物学

Unit 1

第一单元

DNA, Cells, and Evolution

DNA、细胞与进化

KEY TERMS AND CONCEPTS

关键术语与概念

DNA 螺旋

dna structure and base pairing

DNA has a helical structure that helps store genetic information. The double helix is the shape formed by two strands that twist around each other. This structure is a key feature of DNA in cells.

The two strands are held together by base pairing. Bases on one strand match with bases on the other strand in a regular way. This pairing helps keep the DNA molecule stable and organized.

The helix shape also helps explain how DNA fits into chromosomes and carries instructions for living things. By studying the DNA helix, students can connect molecular structure with heredity and genetic information.

DNA Structure and Base Pairing

the dna helix

DNA has a helical structure that helps store genetic information. The double helix is the shape formed by two strands that twist around each other. This structure is a key feature of DNA in cells. The two strands are held together by base pairing. Bases on one strand match with bases on the other strand in a regular way. This pairing helps keep the DNA molecule stable and organized. The helix shape also helps explain how DNA fits into chromosomes and carries instructions for living things. By...

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prokaryotic cells

Inside Prokaryotic Cell Structure

Prokaryotic cells have a simple internal structure compared with many other cells. They are usually divided into two groups: bacteria and archaea. These cells have no nucleus, so their DNA is not enclosed in a membrane-bound compartment. Instead, the genetic material is found in the nucleoid, a region where the DNA is located in the cell. Some prokaryotic cells also contain plasmids, which are small extra DNA molecules. A capsule may surround the cell and provide an additional outer layer. <br...

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Cell Compartments in Eukaryotes

Eukaryotic cells use compartments to organize many different jobs inside one cell. These compartments help separate processes so they can happen in the right place. The compartment called the cytosol is the fluid part of the cell. It surrounds the other internal structures and helps support many cell processes. Inside the cell, membrane-bound organelles create distinct microenvironments. A microenvironment is a small internal space with conditions that fit a specific task. This separation...

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How Mutations Change DNA

Mutations are changes in DNA. They can alter the genetic code and affect how genes work. In high school biology, students often study mutations to understand how DNA changes can influence traits. The transcript focuses on two common mutation types: point mutations and frameshift mutations. A point mutation changes one nucleotide, which is one DNA building block. A frameshift mutation happens when nucleotides are added or removed and the reading frame shifts. These changes matter because they...

gene evolution - fast or slow?

Why Some Gene Regions Evolve Faster

Gene regions do not all change at the same rate. In eukaryotes, long stretches of DNA do not code for proteins or RNAs. Some of these non-coding regions include important regulatory sequences, but most have no known function. Because little or no selection pressure acts on them, they often change the fastest over evolutionary time. Protein-coding regions usually evolve more slowly. A change in a coding sequence can alter a protein and make it less effective at doing its job. That creates...

genome size and the evolution of new genes

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How Genome Size Shapes New Genes

Genome size can vary widely, and it also helps show how new genes form. Every living organism has a genome, whether it uses RNA or DNA. Yet the size of that genome can be very different from one organism to another. One major difference is whether the organism is prokaryotic or eukaryotic. Prokaryotic genomes usually have little to no non-coding sequence, which means genes are packed closely together in operons along the chromosome. Eukaryotic genomes contain long stretches of non-coding DNA...

gene families

How Gene Families Evolve and Diversify

Gene families are groups of genes that are thought to come from a shared ancestor. They usually form when a gene is copied by mistake during cell division. The original gene stays under selection pressure to keep its job, while the extra copy can change more quickly over time. Some copied genes gain a new role in the organism. When that happens, they are called paralogs, which are two genes in the same species that evolved from one common ancestral gene. Gene families also include orthologs,...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

How Genes Move Within and Across Generations

Genetic transfer is the movement of genetic information from one organism to another. It happens in two main ways: vertical gene transfer and horizontal gene transfer. Vertical gene transfer moves genes from one generation to the next. It is much more common than horizontal gene transfer. Vertical gene transfer happens during both sexual reproduction and asexual reproduction. In both cases, one or more organisms pass some or all of their genome to their offspring. This kind of transfer occurs...

key terms and concepts

Explore the DNA double helix and base pairing in a clear, high school-friendly overview of how DNA stores genetic information.

DNA Structure and Base Pairing | JoVE K12

molecular biology

JoVE Core 分子生物学通过清晰简洁的动画视频课程展示了细胞的分子过程。此外，在科学家在行动的视频中，这些概念的应用是通过现代实验室中的真实实验演示的。

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

High School

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

Next Generation Science Standards

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From Molecules to Organisms: Structures and Processes

HS-LS1-1

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-1.

myJoVE Corporation

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1 Exploring phenomena or engineering problems
 1.1 Asking questions and defining problems
  1.1.1 Students will be able to ask questions about aspects of the phenomena they observe, the conclusions they draw from their models or scientific investigations, each other’s ideas, and the information they read.

DNA Structure and Base Pairing

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