A new method provides a three-dimensional identikit of chromosomes
Genome sequencing is a milestone in modern biology as it allows access to the entire "list of instructions" (the chemical sequence of genetic makeup) for the development and function of organisms. Sequencing the genome is a bit like writing down the exact order of the colour of beads in a necklace: knowing how they are arranged along the thread gives us no indication as to the shape of the necklace.
The shape of the DNA strand can be highly complex, given that the chromosomes are loosely arranged in an apparently chaotic tangle in the cell nucleus. Since the shape of chromosomes may have a decisive effect on their function, it is important that it should be characterised, in part because scientists think the DNA tangle in the nucleus is only apparently chaotic and that it has instead a specific "geography" for each tissue and stage of cell life.
"Arriving at a precise description of the shape of the DNA tangle is unfortunately incredibly complicated", explains Cristian Micheletti, SISSA professor and coordinator of the new study. "In our case, we used experimental data on 'proximity pairs'".
"Imagine having to create a map of a city", he explains, "based only on information like 'the post office is opposite the station', 'the chemist is close to the gym', 'the fruit and vegetable market is near the football field' and so on. If you have only a small number of such statements to go by, your map will be approximate and in some cases indeterminate. But if you have hundreds, thousands or even more, then your map will become increasingly precise and accurate. This is the logic we followed".
"Proximity pairs" therefore refers to information on the closeness of two points on the map. In the case of nuclear DNA, this information was provided by a technique (which Micheletti defines as "brilliant") known as Hi-C, developed by North American research groups in 2010. In this chemical-physical technique, bits of genome located close to each another in the nucleus are tied together and then identified by their sequence.
By collecting large numbers of these proximity pairs scientists discovered which points of the chromosomes lie close to each other in the nucleus. While this is today the most powerful technique for investigating DNA organisation in the nucleus, it is still inadequate for inferring its overall shape. "For this reason, we thought we would try to go 'further'", comments Micheletti.
Federica Sgorbissa | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine