Name: how dna structure was discovered
Uploaded: 2023-04-30T10:29:48.000Z
Duration: 1 min 7 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

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

From Molecules to Organisms- Structures and Processes

LS.Bio.1.5

The DNA Helix

L’acide désoxyribonucléique, ou ADN, est constitué de deux chaînes polynucléotidiques.
Chacune de ces chaînes est composée de quatre types de sous-unités nucléotidiques.
Chaque nucléotide se compose d’un seul groupe phosphate et d’une base contenant de l’azote - adénine, A, cytosine, C, guanine, G ou thymine, T, attachée à un sucre désoxyribose.
Cet arrangement crée le squelette sucre-phosphate de la structure de l’ADN.
Le long de l’épine dorsale de chaque brin, les liaisons phosphodiester lient de manière covalente le troisième atome de carbone d’un sucre au cinquième atome de carbone de la molécule de sucre suivante dans la chaîne.
Dans les brins antiparallèles opposés, chaque base est appariée de manière unique, C avec G et A avec T, en raison des différences dans le nombre de liaisons hydrogène qui se forment entre elles.
Une telle polarité chimique assure un compactage efficace, enroulant les deux brins l’un autour de l’autre pour former une double hélice 3D, avec dix paires de bases tous les tours complets.

l'hélice d'adn

L'acide désoxyribonucléique, ou ADN, est le matériel génétique responsable de la transmission des caractères de génération en génération dans tous les organismes et dans la plupart des virus. L'ADN est composé de deux brins de nucléotides qui s'enroulent l'un autour de l'autre pour former une structure en forme de ressort appelée double hélice. Cependant, la double hélice n’est pas parfaitement symétrique. Au lieu de cela, des rainures apparaissent régulièrement dans la structure. Le sillon principal se produit là où les squelettes sucre-phosphate sont relativement éloignés les uns des autres. Cet espace donne accès aux protéines liant l’ADN, telles que les facteurs de transcription. Le petit sillon, en revanche, se produit là où les squelettes sucre-phosphate sont rapprochés. Relativement peu de protéines se lient à l’ADN via le petit sillon.

La Découverte de La structure de l'ADN : Une Brève Histoire

La découverte de la structure de l’ADN s’est produite progressivement sur près d’un siècle, représentant l’une des histoires les plus célèbres et captivantes de l’histoire de la science.

Tout a commencé en 1869 lorsque le scientifique suisse Friedrich Miescher a découvert une substance qu'il a appelée « nucléine ». En extrayant les protéines des globules blancs, Miescher a découvert une substance inattendue dont la teneur en phosphore était relativement élevée. Il ne savait pas ce que c'était, mais il soupçonnait que cela pouvait être biologiquement important. Miescher avait raison, mais il a fallu des décennies pour que la communauté scientifique apprécie pleinement ses idées.

La découverte critique suivante a été faite par le biochimiste russe Phoebus Levene. En 1919, Levene a proposé que la nucléine, alors connue sous le nom d’acide nucléique, soit composée de chaînes de molécules qu’il appelait polynucléotides. La proposition de Levene découle de ses recherches sur la levure, dans lesquelles il a découvert que les nucléotides individuels étaient composés d'un groupe phosphate, d'un sucre et d'une base contenant de l'azote. Bien que le modèle polynucléotidique de Levene soit correct à bien des égards, la manière dont les bases étaient disposées dans la molécule d'ADN n'était toujours pas claire.

Le biochimiste autrichien Erwin Chargaff a développé les travaux de Levene. Travaillant à la fin des années 1940, Chargaff a fait une découverte clé : la quantité d’adénine dans l’ADN est toujours à peu près égale à la quantité de thymine, et la quantité de guanine est toujours à peu près égale à la quantité de cytosine. Ce modèle est devenu connu sous le nom de règle de Chargaff et a été un élément de preuve clé qui a permis l'élucidation finale de la structure de l'ADN.

Au début des années 1950, le biologiste américain James Watson et le physicien anglais Francis Crick faisaient la course avec leur principal rival, l'Américain Linus Pauling, pour découvrir la structure tridimensionnelle de l'ADN. S'appuyant sur les travaux de Chargaff, ils ont utilisé leurs connaissances en physique, mathématiques et chimie pour construire des modèles physiques de l'ADN. Mais ils n’y parviennent pas jusqu’à ce qu’ils reçoivent une donnée cruciale : une « photographie » aux rayons X de l’ADN qui indiquait avec précision sa structure en double hélice. Cette photographie était une donnée inédite de la physicienne Rosalind Franklin et a été donnée à Watson et Crick à l'insu de Franklin. Watson et Crick ont publié leur description de la structure de l'ADN en 1953 et, avec Maurice Wilkins (un collègue de Franklin), ils ont remporté le prix Nobel de physiologie ou médecine en 1962 pour cette découverte. Malheureusement, Franklin est décédé en 1958 et n’était donc pas éligible au prix Nobel.

L'hélice d'ADN

L’acide désoxyribonucléique, ou ADN, est le matériel génétique responsable de la transmission de traits de génération en génération dans tous les organismes et la plupart des virus. ADN...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Cells, Genomes, and Evolution

Cellules, génomes et évolution

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how dna structure was discovered

DNA is the genetic material that passes traits from one generation to the next in organisms and most viruses. It is made of two strands of nucleotides that twist into a spring-like double helix. The shape is not perfectly even. It also has repeating grooves called the major groove and the minor groove.

The major groove forms where the sugar-phosphate backbones are farther apart. This wider space gives DNA-binding proteins, including transcription factors, better access to the bases. The minor groove forms where the backbones are closer together. Relatively few proteins bind to DNA through the minor groove.

The story of DNA structure unfolded over nearly a century. It began in 1869, when Swiss scientist Friedrich Miescher found a phosphorus-rich substance in white blood cells and called it nuclein. He did not know what it was, but he suspected it had biological importance. Later work showed that his idea was right.

In 1919, Russian biochemist Phoebus Levene proposed that nucleic acid was made of chains of molecules called polynucleotides. His yeast studies showed that each nucleotide contains a phosphate group, a sugar, and a nitrogen-containing base. This model was useful, but it still did not explain how the bases were arranged in DNA. In the late 1940s, Erwin Chargaff added a key clue by showing that adenine is roughly equal to thymine and guanine is roughly equal to cytosine.

That evidence helped James Watson and Francis Crick build their DNA models in the early 1950s. They were competing with Linus Pauling and used ideas from physics, mathematics, and chemistry. They succeeded only after seeing an X-ray photograph of DNA that showed the double helix in detail. The image came from Rosalind Franklin’s unpublished data and was shared without her knowledge. Watson and Crick published their description in 1953, and with Maurice Wilkins they received the 1962 Nobel Prize in Physiology or Medicine. Franklin died in 1958, so she was not eligible for the prize.

How DNA Structure Was Discovered

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the nucleus

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the dna helix

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gene families

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gene evolution - fast or slow?

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types of genetic transfer between organisms

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key terms and concepts

Explore how scientists uncovered DNA’s double helix, from Miescher’s nuclein to Chargaff’s rule, Franklin’s X-ray image, and Watson and Crick.

How DNA Structure Was Discovered | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Pennsylvania State Academic Standards

Life Science

Inheritance and Variation of Traits

3.1.9-12.P

3.1.9-12.Q

Louisiana Student Standards for Science

High School

Life Sciences

From Molecules To Organisms: Structures And Processes

HS-LS1-1

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance And Variation Of Traits

HS-LS3-1

Biological Evolution: Unity And Diversity

HS-LS4-1

Tennessee Academic Standards

From Molecules to Organisms: Structures and Processes

BIO1.LS1.3

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HIgh School

BIO.2

BIO.2.d

BIO.5

BIO.5.b

Minnesota Academic Standards in Science

3.1.1 9L.3.1.1.4

Florida Department of Education

SC.912.L.16

SC.912.L.16.4

SC.912.L.18

SC.912.L.18.1

Texas Essential Knowledge and Skills

BIO.7

BIO.7.A

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South Carolina College and Career Ready Science Standards

B-LS1-1.

Heredity: Inheritance and Variation of Traits

B-LS3-1.

Georgia Standards of Excellence

SB6.c

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LS.Bio.1.2

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LS.Bio.1.3

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How DNA Structure Was Discovered

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