Scientists Seek Ban on Method of Editing the Human Genome Photo A group of leading biologists on Thursday called for a worldwide moratorium on use of a new genome-editing technique that would alter human DNA in a way that can be inherited. The biologists fear that the new technique is so effective and easy to use that some physicians may push ahead before its safety can be assessed. “You could exert control over human heredity with this technique, and that is why we are raising the issue,” said David Baltimore, a former president of the California Institute of Technology and a member of the group whose paper on the topic was published in the journal Science. Ethicists, for decades, have been concerned about the dangers of altering the human germline — meaning to make changes to human sperm, eggs or embryos that will last through the life of the individual and be passed on to future generations. The technique holds the power to repair or enhance any human gene. There are two broad schools of thought on modifying the human germline, said R. Photo
Cell Size and Scale Some cells are visible to the unaided eye The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that under the right conditions, you might be able to see an amoeba proteus, a human egg, and a paramecium without using magnification. A magnifying glass can help you to see them more clearly, but they will still look tiny. Smaller cells are easily visible under a light microscope. To see anything smaller than 500 nm, you will need an electron microscope. Adenine The label on the nucleotide is not quite accurate. How can an X chromosome be nearly as big as the head of the sperm cell? No, this isn't a mistake. The X chromosome is shown here in a condensed state, as it would appear in a cell that's going through mitosis. A chromosome is made up of genetic material (one long piece of DNA) wrapped around structural support proteins (histones). Carbon The size of the carbon atom is based on its van der Waals radius.
« La notion de programme génétique est morte » | Usbek & Rica Toutes nos excuses. Nous vous proposions récemment une liste des raisons pour lesquelles 2016 restera comme une année historique dans un siècle. Mais nous avons oublié la principale : l’étude sur la différenciation cellulaire publiée le 27 décembre 2016 dans la revue PLOS Biology, qui remet en cause le rôle des gènes dans notre compréhension du vivant. Rien que ça. Cette découverte pourrait chambouler la science, la médecine, la philosophie, voire l'industrie. Explications. Vous, moi, Mère Teresa et Chuck Norris avons tous un point commun : les organismes vivants prodigieux de complexité que nous sommes n’étaient, à l’origine, qu’une minuscule et unique cellule-œuf. « Lorsqu’on a entrepris de séquencer le génome, on a promis qu’il serait le grand livre de la vie, qu’il expliquerait tout. « Le génome a été survendu, affirme Olivier Gandrillon, chercheur au Laboratoire de biologie et modélisation de la cellule. Darwin version différenciation cellulaire Causalité circulaire et environnement
Human Embryo Editing Sparks Epic Ethical Debate In a world first, Chinese scientists have reported that they have used powerful gene-editing techniques to modify human embryos. Their paper, published in the Beijing-based journal Protein & Cell on April 18, came as no surprise to the scientific community, but it has ignited a wide-ranging debate about what types of gene-editing research are ethical. The publication also raises questions about the appropriate way to publish such work. In the paper, researchers led by Junjiu Huang, a gene-function researcher at Sun Yat-sen University in Guangzhou, describe how they used a system of molecules called CRISPR/Cas9, known for its ease of use, to cut DNA in human embryos and then attempted to repair it by introducing new DNA. In a deliberate attempt to head off ethical concerns, the team used non-viable embryos obtained from fertility clinics, in which eggs had been fertilized by two sperm and so could not result in a live birth. Modifying human embryos is legal in China and in many US states.
Épigénétique Un article de Wikipédia, l'encyclopédie libre. L'épigénétique est l'ensemble des mécanismes moléculaires concernant le génome ainsi que l'expression des gènes, qui peuvent être influencés par l'environnement et l'histoire individuelle. Ces mécanismes peuvent être potentiellement transmissibles d'une génération à l'autre, sans altération des séquences nucléotidiques (ADN), et avec un caractère réversible. L'existence de phénomènes agissant sur l'expression des gènes se résume dans l'interrogation de Thomas Morgan « Si les caractères de l'individu sont déterminés par les gènes, pourquoi toutes les cellules d'un organisme ne sont-elles pas identiques ? Les différences qui existent entre chaque cellule d'un même organisme ayant le même patrimoine génétique - mis à part quelques rares mutations somatiques - montrent une expression différentielle des gènes. Des phénomènes épigénétiques ont été mis en évidence chez des eucaryotes et des procaryotes. Épigénome[modifier | modifier le code]
New Discovery Moves Gene Editing Closer to Use in Humans A tweak to a technique that edits DNA with pinpoint precision has boosted its ability to correct defective genes in people. Called CRISPR, the method is already used in the lab to insert and remove genome defects in animal embryos. But the genetic instructions for the machinery on which CRISPR relies—a gene-editing enzyme called Cas9 and RNA molecules that guide it to its target—are simply too large to be efficiently ferried into most of the human body’s cells. This week, researchers report a possible way around that obstacle: a Cas9 enzyme that is encoded by a gene about three-quarters the size of the one currently used. The finding, published on 1 April in Nature, could open the door to new treatments for a host of genetic maladies (F. A. “There are thousands of diseases in humans associated with specific genetic changes,” says David Liu, a chemical biologist at Harvard University in Cambridge, Massachusetts, who was not involved in the latest study.
Siddhartha Mukherjee | THE GENE: An Intimate History