Name: chargaff’s rules and dna pairing
Uploaded: 2020-09-24T15:06:53.000Z
Duration: 2 min 27 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-1

DNA Base Pairing

DNA, bükülmüş bir merdivene benzer. Ve DNA merdiveninin basamakları, birbirini tamamlayan nitrojenli baz çiftleridir. Baz eşleştirme kurallarına göre, bir pürin olan adenin, iki hidrojen bağına sahip bir pirimidin olan timin ile eşleşir.Ve bir purin olan guanin, üç hidrojen bağına sahip bir pirimidin olan sitozin ile birlikte ortaya çıkar. Peki pürinler neden her zaman pirimidinlerle eşleşir? DNA'nın şeker fosfat omurgası tarafından uygulanan uzamsal kısıtlamalar olan sterik kısıtlamalar nedeniyle, bir DNA çift sarmalındaki baz çiftleri için yalnızca 10, 85 angstrom boşluk mevcuttur.Purinlerin çift halkalı bir yapısı vardır. Bu nedenle, iki pürin birlikte bu boşluğa sığmayacak kadar büyük olacaktır. Öte yandan, yalnızca tek bir halka içeren iki pirimidini bir araya getirirsek, aralarındaki mesafe, yaklaşık olarak iki angstrom uzunluğunda olan hidrojen bağları oluşturmak için çok büyük olacaktır.Bununla birlikte, bir pürin ve bir pirimidin eşleştirirsek, DNA sarmalının içine mükemmel bir şekilde uyarlar ve hidrojen bağları oluşturacak kadar yakındırlar. Bir hidrojen atomu, oksijen veya nitrojen gibi bir elektronegatif atomdan yaklaşık iki angstrom uzakta olduğunda hidrojen bağları oluşabilir. Adenine bir oksijen ve timine yakın bir hidrojen atomuna sahiptir.Ve timin bir nitrojen ve adenine yakın bir hidrojene sahiptir. Bu, iki hidrojen bağının oluşumuna yol açar. Adenin, sitozin ile hidrojen bağları oluşturamaz çünkü sitozin, oksijen ve timinin olacağı yerde bir hidrojen atomuna sahiptir.Ve timinde bulunan hidrojen atomu sitozinde yoktur. Guanin içindeki bir oksijen ve sitozindeki bir oksijen e bir nitrojenin her birinin bir hidrojenin karşısında konumlandığı guanin sitozin baz çiftinde benzer bir fenomen meydana gelir ve guanin timin baz eşleşmesinde meydana gelmeyen üç hidrojen bağı oluşumuna yol açar. DNA replikasyon enzimlerinin yardımıyla baz eşleştirmesinin yüksek özgüllüğü, adeninin her zaman timinle ve guaninin her zaman sitozinle eşleşmesinin nedenidir.

dna bazlarının eşleştirilmesi

Erwin Chargaff'ın DNA denkliği ile ilgili kuralları, DNA'daki baz eşleşmesinin keşfinin yolunu açtı. Chargaff'ın kuralları, çift sarmallı bir DNA molekülünde,
 <ol>
 <li>adenin (A) miktarı, timin (T) miktarına eşittir;</li>
 <li>guanin (G) miktarı, sitozin (C) miktarına eşittir; ve</li>
 <li>pürinlerin toplamı, A ve G, pirimidinler, C ve T'nin toplamına eşittir (yani, A+G = C+T).</li>
 </ol>
 
 Watson ve Crick'in daha sonraki çalışmaları, çift sarmallı DNA'da, A'nın her zaman T ile iki hidrojen bağı oluşturduğunu ve G'nin her zaman C ile üç hidrojen bağı oluşturduğunu ortaya koydu. Bu baz çifti, hem A-T hem de C-G çiftleri 10,85Å uzunluğunda olduğundan ve iki şeker-fosfat omurgası arasında düzgün bir şekilde oturduğundan, DNA çift sarmalının sabit bir genişliğini korur.
 
 Baz eşleşmeleri, hidrojen bağları ayrılıncaya kadar azotlu bazların diğer moleküllere erişilememesine neden olur. Bununla birlikte, spesifik enzimler, DNA replikasyonu ve transkripsiyon gibi gerekli hücre işlemlerini gerçekleştirmek için bu hidrojen bağlarını kolayca kırabilir. Bir G-C çifti,  bir A-T çiftinden daha fazla hidrojen bağına sahip olduğundan, yüksek bir G-C çift yüzdesine sahip DNA, iki DNA ipliğinin ayrılması için benzer bir A-T çift yüzdesine sahip olandan daha yüksek enerjiye ihtiyaç duyacaktır. 
 
 İlaç Olarak Baz Analogları
 
 DNA'nın yanlışsız replikasyonu için doğru baz eşleşmesi gereklidir. Baz analogları, DNA replikasyonu sırasında standart DNA bazlarının yerini alabilen moleküllerdir. Bu analoglar, hepatit, herpes ve lösemi gibi hastalıklara karşı etkili antiviral ve antikanser ajanlardır. Asikloguanozin olarak da bilinen asiklovir, guaninin baz analoğudur ve herpes simpleks virüsünün tedavisinde yaygın olarak kullanılır. Asiklovirin guanin kısmı, DNA replikasyonu sırasında her zamanki gibi adenin ile çiftleşir; bununla birlikte, nükleotidin 3’ ucuna sahip olmadığı için, DNA polimeraz baz çiftleri oluşturmaya devam edemez ve replikasyon sona erer.

DNA Bazlarının Eşleştirilmesi

Erwin Chargaff'ın DNA denkliği ile ilgili kuralları, DNA'da baz eşleşmesinin keşfinin yolunu açtı. Chargaff'ın kuralları, bir ...

Education

JoVE Core

Chemistry

Kimya

Biochemistry

Biyokimya

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

chargaff’s rules and dna pairing

Chargaff’s rules and DNA base pairing explain how DNA strands match up. In double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Chargaff also found that A equals T, G equals C, and the total amount of purines (A and G) equals the total amount of pyrimidines (C and T).

Watson and Crick later showed why these matches matter. A forms two hydrogen bonds with T, while G forms three hydrogen bonds with C. These pairings keep the DNA double helix a constant width because both A-T and C-G pairs fit neatly between the two sugar-phosphate backbones.

Base pairing also keeps the nitrogenous bases hidden from other molecules until the hydrogen bonds separate. Specific enzymes can break these bonds when the cell needs to copy DNA or make RNA during transcription. DNA with more G-C pairs usually needs more energy to separate than DNA with more A-T pairs, because G-C pairs have more hydrogen bonds.

Correct pairing is also important in medicine. Base analogs are molecules that can replace normal DNA bases during replication, and they can act as antiviral or anticancer drugs against diseases such as hepatitis, herpes, and leukemia. Acyclovir, also called acycloguanosine, is a guanine analog used to treat herpes simplex virus. It pairs with adenine, but it lacks a 3' end, so DNA polymerase cannot keep building the strand and replication stops.

Chargaff’s Rules and DNA Pairing

functional groups

Functional Groups in Organic Chemistry

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chemistry of the cell

Cell Chemistry: Water and Macromolecules

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dna base pairing

Chargaff’s rules and DNA base pairing explain how DNA strands match up. In double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Chargaff also found that A equals T, G equals C, and the total amount of purines (A and G) equals the total amount of pyrimidines (C and T). Watson and Crick later showed why these matches matter. A forms two hydrogen bonds with T, while G forms three hydrogen bonds with C. These pairings keep the DNA double helix a...

chemistry of carbohydrates

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protein and protein structure

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amino acids

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peptide bonds

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polymers

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Polymers are long chains of molecules made from repeating units called monomers. The word polymer comes from the Greek words "poly," meaning many, and "mer," meaning parts. Polymers can be found in nature, such as DNA and proteins, or made synthetically, such as plastics. A polymer’s shape helps define its properties. Some polymers form linear chains, while others are branched or arranged in complex networks. Functional groups on a polymer also affect how it behaves. The repeating units in a...

key terms and concepts

Learn how Chargaff’s rules, hydrogen bonding, and base analogs like acyclovir help explain DNA pairing, replication, and antiviral treatment.

Chargaff’s Rules and DNA Pairing | JoVE K12

chemistry

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Tennessee Academic Standards

Biology

From Molecules to Organisms: Structures and Processes

BIO1.LS1.3

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South Carolina College and Career Ready Science Standards

B-LS1-1.

Nucleic Acids and Nucleotides

Nucleic acids are the most important macromolecules for the continuity of life. They carry the cell&#39;s genetic blueprint and have instructions for its ...

Nucleic Acid Structure

The pentose sugar in DNA is deoxyribose, while in RNA the pentose sugar is ribose. The difference between the sugars is the presence of the hydroxyl group ...

Erwin Chargaff&#x2019;s rules on DNA equivalence paved the way for the discovery of base pairing in DNA. Chargaff&#x2019;s rules state that in a ...

From DNA to Protein

The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of ...

The DNA Helix

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most viruses. DNA ...

The Central Dogma

The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
RNA is the Missing Link Between ...

Genomic DNA in Prokaryotes

The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the ...

Genomic DNA in Eukaryotes

Eukaryotes have large genomes compared to prokaryotes. To fit their genomes into a cell, eukaryotic DNA is packaged extraordinarily tightly inside the ...

Overview

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most ...

DNA Packaging

Overview

Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside ...

RNA Structure

Overview
The basic structure of RNA consists of a five-carbon sugar and one of four nitrogenous bases. Although most RNA is single-stranded, it can form ...

RNA Stability

Intact DNA strands can be found in fossils, while scientists sometimes struggle to keep RNA intact under laboratory conditions. The structural variations ...

pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or ...

Types of RNA

Overview
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs ...

DNA as a Genetic Template

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

tRNA Activation

Initiation of Translation

Termination of Translation

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cells of the Epidermis

The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the ...

Bone Cells and Tissue

Bones contain a relatively small number of cells entrenched in a matrix of organic and inorganic components. Although bone cells compose only a small ...

Gross Anatomy of Skeletal Muscles

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Structure of Cardiac Muscles

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structure-and-organization-of-smooth-muscles

Structure and Organization of Smooth Muscles

In the human body, smooth muscle tissue is found lining the visceral and tubular organs such as the liver, lungs, blood vessels, and respiratory tract.
...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

Neurons: The Cell Body and the Dendrites

A typical nerve cell comprises three main components: the cell body, dendrites, and the axon. The cell body, also known as the soma or perikaryon, serves ...

Lampbrush Chromosomes

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Neurons: The Axon

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Polytene Chromosomes

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Nervous Tissue: Neuron Types

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Structurally, ...

Euchromatin

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Nervous Tissue: Glial Cells

Glial cells or neuroglia are non-neuronal cells in the nervous system that outnumber neurons. These include astrocytes, oligodendrocytes, microglia, and ...

Heterochromatin

Lymphoid Cells and Tissues

Lymphoid cells and lymphoid tissues are the two major components of lymphoid organs.
Lymphoid cells consist of immune system cells such as B and T ...

chromatin-position-affects-gene-expression

Chromatin Position Affects Gene Expression

Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the ...

Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The ...

Organization of Genes

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells. Emphasis is on the conceptual understanding that DNA sequences determine the amino acid sequence and thus protein structure. Students can produce scientific writing, or presentations, and/or physical models that communicate constructed explanations.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Levels of Organization

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth&#x27;s biosphere. ...

The Scientific Method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves ...

Taxonomy

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics. It uses a hierarchy of increasingly ...

Phylogeny

Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon ...

Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, or organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.

HS-LS1-2

Overview of Metabolism

Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one ...

Regulation of Metabolism

Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, the required enzymes and energetic demands ...

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis (&#34;steady state&#34;). Examples ...

Functions of Life

Human life is characterized by a variety of functions that are essential for survival and well-being. These functions include metabolism, movement, ...

Requirements for Human Life

The Earth and its atmosphere have provided humans with air, water, and food, but these are not the only requirements for survival. Humans also require a ...

What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Negative and Positive Feedback

Homeostatic Imbalance

Homeostasis is the maintenance of a stable internal environment within the body, which is crucial for the proper functioning of cells, tissues, organs, ...

pH Homeostasis

Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because ...

homeostatic-imbalances-in-body-temperature

Homeostatic Imbalances in Body Temperature

Hyperthermia is an umbrella term for elevated body temperature that occurs when heat production exceeds the body&#39;s ability to dissipate it.
...

Regulation of Food Intake

The hypothalamus releases peptides influencing feeding behavior.
Two hypothalamic neuronal groups participate in this process.
Neuropeptide Y (NPY) and ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis in living organisms. Examples of investigations could include heart rate responses to exercise, stomate responses to moisture and temperature, root development in response to water levels, or cell response to hypertonic and hypotonic environments.

HS-LS1-3

What is the Cell Cycle?

The cell cycle refers to the sequence of events occurring throughout a typical cell&#8217;s life. In eukaryotic cells, the somatic cell cycle has two ...

Interphase

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the ...

The Cell Cycle Control System

Positive Regulator Molecules

Inhibition of CDK Activity

S-Cdk Initiates DNA Replication

M-Cdk Drives Transition Into Mitosis

Mitogens and the Cell Cycle

Replicative Cell Senescence

Abnormal Proliferation

cells-coordinate-growth-and-proliferation

Cells Coordinate Growth and Proliferation

Use a model to illustrate the role of the cell cycle and differentiation in producing and maintaining complex organisms. Emphasis is on conceptual understanding that mitosis passes on genetically identical materials via replication, not on the details of each phase in mitosis.

HS-LS1-4

Chargaff’s Rules and DNA Pairing

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