Human males have both a X and a Y chromosome but females have two X chromosomes. This means that in an early stage in the development of a woman’s fertilised egg the cells need to silence one of those two X chromosomes. This process is crucial to survival and problems with the process are related to serious genetic diseases.
Both X chromosomes in a cell have a suicide gene called XIST which, if activated, seals the chromosome behind a barrier of RNA preventing the activation of any other gene. Researchers believe that this suicide gene can be itself blocked by a plug of proteins forming on top of its specific location on the chromosome but they had little idea as to why this should happen randomly to one X chromosome’s gene and not the other.
Scientists are extremely uncomfortable with this randomness and have sought a clear scientific reason as to why one X chromosome was switched off rather than the other. The observations also seem to run counter to the usual idea that the biological mechanisms evolve in ways that allow a "best" choice to be made between things rather than a random one.
Now researchers led by University of Warwick physicist Dr Mario Nicodemi have explained how this randomness occurs and why that it is beneficial. This will help understand the problems of a small number of women who unusually don’t have a completely random distribution of X chromosomes but the explanation may have much wider implications as at least 10% of our genes may behave in similar ways as mechanism that "chooses" between X chromosomes. Examples of this range from the immune system to our olfactory apparatus.
Coming at the problem from the perspective of a physicist Dr Nicodemi has found an explanation for the random selection based on thermodynamics. Research has already shown that at the key moment in this process both X chromosomes are brought close together within the cell. The Warwick researcher paper says that what happens next is that material for a "protein plug" then begins to gather around both of the XIST suicide genes on each X Chromosome. This starts a race between the two build ups of protein. Inevitably one of these two nascent protein plugs narrowly wins that race and reaches an energy state in which it can pull together all the material building up in both plugs into a single protein plug. That single plug then closes off one of the XIST suicide genes allowing its host X chromosome to continue to operate. However the other XIST suicide gene is now freed to activate and shuts down its X chromosome.
Since putting forward this explanation researchers in Harvard have observed actual plugs of protein shutting down X chromosome XIST genes in a manner giving further confirmation to Dr Nicodemi’s research. So the randomness is explained but what about researchers’ other concerns? Dr Nicodemi believes the randomness actually does give an evolutionary advantage. The mechanism means equal numbers of both the maternal and paternal X chromosome are preserved in the gene pool and the resultant population thus has more chance of surviving any biological threat targeted at a single version of the X chromosome.
Peter Dunn | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
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
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences