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94 notes
22 avis
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Anglais

Sous-titres : Anglais
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100 % en ligne

Commencez dès maintenant et apprenez aux horaires qui vous conviennent.
Dates limites flexibles

Dates limites flexibles

Réinitialisez les dates limites selon votre disponibilité.
Heures pour terminer

Approx. 27 heures pour terminer

Recommandé : 4 hours/week...
Langues disponibles

Anglais

Sous-titres : Anglais

Programme du cours : ce que vous apprendrez dans ce cours

Semaine
1
Heures pour terminer
2 heures pour terminer

Session 1

At the dawn of genetics, in the work of Mendel and Morgan, there was a complete void between the genes and the characters they determine.During the first week, we will discuss the relationship between genes and enzymes. We will start with the description of alkaptonuria by Garrod, in 1902, which he called a few years later an inborn error of metabolism. This was the first documented example of a human recessive trait, the first association of a human condition with Mendel’s principles and the first link between a gene and an enzyme. This work and that of Cuénot on mice fur color were essentially forgotten in the biology community in the following decades.After working with great difficulty on the enzymatic cascade that leads to the formation of the pigmented eye of fruit flies, Beadle and Tatum founded the field of biochemical genetics by isolating conditional mutants that affect the synthesis of vitamins and amino acids. This was first done with a mold, and then extended to bacteria. These experiments lead to the “one gene, one enzyme” hypothesis. While the hypothesis is now proven in many cases, the exceptions, including multigene enzymes, structural and enzymatic RNAs have expanded the concept rather than invalidating it....
Reading
7 vidéos (Total 107 min), 2 lectures, 1 quiz
Video7 vidéos
Part 1 - Perspective11 min
Part 214 min
Part 316 min
Part 425 min
Part 526 min
Part 67 min
Reading2 lectures
Figures in this module10 min
Readings (to be read before lectures 4-6)10 min
Quiz1 exercice pour s'entraîner
Beadle & Tatum10 min
Semaine
2
Heures pour terminer
2 heures pour terminer

Session 2

Most people believed that genes must be made of proteins because nucleic acids were considered too simple to carry genetic information. Avery worked all his life on Pneumococcus and bacterial pneumonia. Griffith showed that transformation of a non-virulent strain can be achieved in mice by coinjection of heat-killed virulent bacteria. Avery’s lab managed to obtain transformation in the test tube, but it took many years to establish a reliable assay and finally to purify the molecule responsible for this effect, which turned out to be DNA. Although this work was well known, most scientists were not convinced of the general implication of this phenomenon. Furthermore, many biochemists believed that even the purified DNA was contaminated with a protein. Finally, transformation was a very inefficient process and the mechanism of transformation remained mysterious for many years. The work of Hershey and Chase finally convinced the scientific community that genes are made of DNA. We now realize that exchange of DNA by transformation is very common, and participates to the horizontal transfer of DNA between at least bacterial species, and was a considerable accelerator of evolution ...
Reading
7 vidéos (Total 95 min), 2 lectures, 1 quiz
Video7 vidéos
Part 118 min
Part 213 min
Part 39 min
Part 413 min
Part 511 min
Part 610 min
Part 7 - Quantitative analysis of transformation19 min
Reading2 lectures
Figures in this module10 min
Readings (to be read before lectures 4-6)10 min
Quiz1 exercice pour s'entraîner
Avery Questions20 min
Semaine
3
Heures pour terminer
2 heures pour terminer

Session 3

The origin of mutations was a field of heavy discussions between proponents of Darwinism and those of Lamarckism. The major issue was to define an experimental approach that would unambiguously discriminate between mutations occurring at random and mutations caused by the selective agent used to reveal their existence. In the case of bacteria that became resistant to the lytic action of a bacteriophage, the hypotheses were labeled “mutation to immunity” versus “acquired immunity”. Luria and Delbrück realized that the variations observed in the number of resistant bacteria in different parallel cultures were intimately linked to the mutation hypothesis. This exceptional collaboration between a theoretical physicist and a bacteriologist is a perfect example of interdisciplinary work, while these two “enemy aliens” were working in the USA. At that time, it was not even clear that bacteria had genes and most bacteriology work was only descriptive. The use of a quantitative approach allowed the authors to settle the question. The fluctuation test is a very powerful tool to calculate mutation rates. Soon after, Newcombe did a simple but elegant experiment to demonstrate that the increased number of resistant bacteria that are detected upon clonal expansion reflects both the amplification of preexisting mutants and the continuous occurrence of new mutations. ...
Reading
4 vidéos (Total 77 min), 2 lectures, 1 quiz
Video4 vidéos
Part 125 min
Part 213 min
Part 37 min
Part 430 min
Reading2 lectures
Figures in this module10 min
Readings: Read the papers before watching Part 3 & Part 410 min
Quiz1 exercice pour s'entraîner
Origin of mutations14 min
Semaine
4
Heures pour terminer
2 heures pour terminer

Session 4

When DNA was found to be the genetic material, it was not known how this molecule could carry information. The structure of DNA thus became of critical importance. The available X-ray images obtained by M. Wilkins and R. Franklin only yielded a rough picture, and even R. Franklin, who had the clearest diffraction data, could not decide whether the molecules contained two or three strands. Both Pauling and Watson and Crick used molecular models with known inter-nuclear distances (bond length) and bond angles to predict a structure. While the model of Pauling was hardly realistic, since it used the protonated form of the phosphate, the model proposed by Watson and Crick proposed that DNA consists of a pair of DNA strands. Furthermore, it indicated that any nucleotide sequence could be accommodated in the structure. The only central biological issue that was addressed in the first paper was replication, and the famous sentence was really nothing more than a priority claim. Much more biology was discussed in the second paper. It was assumed that base pairing is sufficient to account for the fidelity of replication. The importance of DNA polymerase in replication fidelity was first demonstrated by Speyer....
Reading
5 vidéos (Total 69 min), 2 lectures, 1 quiz
Video5 vidéos
Part 115 min
Part 27 min
Part 313 min
Part 423 min
Part 58 min
Reading2 lectures
Figures in this module10 min
Read the papers before watching parts 3 to 510 min
Quiz1 exercice pour s'entraîner
DNA structure and the fidelity of replication14 min
4.7
22 avisChevron Right

Meilleurs avis

par BSMar 25th 2016

Outstanding: the classic papers are always the best primary source of information!

par SWJun 1st 2016

Very cool. Love to hear about these scientists and their lives and efforts

Enseignant

Avatar

Dominique Belin

Professor
Department of Pathology and Immunology University of Geneva Medical School

À propos de University of Geneva

Founded in 1559, the University of Geneva (UNIGE) is one of Europe's leading universities. Devoted to research, education and dialogue, the UNIGE shares the international calling of its host city, Geneva, a centre of international and multicultural activities with a venerable cosmopolitan tradition....

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