 |
|
Physicist cracks women's random but always lucky choice of X chromosome
June 13, 2007A University of Warwick physicist has uncovered how female cells are able to choose randomly between their two X chromosomes and why that choice is always lucky.
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.
University of Warwick
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.
University of Warwick
Chromosome Current Events and Chromosome News RSSNew map of variation in maize genetics holds promise for developing new varieties
A new study of maize has identified thousands of diverse genes in genetically inaccessible portions of the genome. New techniques may allow breeders and researchers to use this genetic variation to identify desirable traits and create new varieties that were not easily possible before.
New Down syndrome treatment suggested by Stanford/Packard study in mice
At birth, children with Down syndrome aren't developmentally delayed. But as they age, these kids fall behind. Memory deficits inherent in Down syndrome hinder learning, making it hard for the brain to collect experiences needed for normal cognitive development.
Cognitive dysfunction reversed in mouse model of Down syndrome
A study by neuroscientist William C. Mobley, MD, PhD, chair of the Department of Neurosciences at the University of California, San Diego School of Medicine, and colleagues at Stanford University Medical School has demonstrated a possible new approach to slowing the inevitable progression of cognitive decline found in Down's syndrome.
Chromosomes dance and pair up on the nuclear membrane
Meiosis - the pairing and recombination of chromosomes, followed by segregation of half to each egg or sperm cell - is a major crossroads in all organisms reproducing sexually.
Largest gene study of childhood IBD identifies 5 new genes
In the largest, most comprehensive genetic analysis of childhood-onset inflammatory bowel disease (IBD), an international research team has identified five new gene regions, including one involved in a biological pathway that helps drive the painful inflammation of the digestive tract that characterizes the disease.
CSHL study shows that some malignant tumors can be shut down after all
Oncologists have had their hands tied because more than half of all human cancers have mutations that disable a protein called p53.
Possible help in fight against muscle-wasting disease
A compound already used to treat pneumonia could become a new therapy for an inherited muscular wasting disease, according to researchers at the University of Oregon and the University of Rochester School of Medicine and Dentistry in New York.
Developmental delay could stem from nicotinic receptor deletion
The loss of a gene through deletion of genetic material on chromosome 15 is associated with significant abnormalities in learning and behavior, said a consortium of researchers led by Baylor College of Medicine (www.bcm.edu) in a report that appears online today in the journal Nature Genetics.
Autism Consortium symposium draws record number of researchers, advocates, parents for autism update
The Autism Consortium, an innovative collaboration of researchers, clinicians, funders and families dedicated to catalyzing research and enhancing clinical care for autism spectrum disorders (ASDs), held its fourth annual symposium on October 28th, 2009, at Harvard Medical School in Boston.
Clinical tests begin on medication to correct Fragile X defect
NIH-supported scientists at Seaside Therapeutics in Cambridge, Mass., are beginning a clinical trial of a potential medication designed to correct a central neurochemical defect underlying Fragile X syndrome, the most common inherited cause of intellectual disability.
More Chromosome Current Events and Chromosome News Articles
 |
Chromosome 6 by Robin Cook (Author) In his most prophetic novel, Robin Cook challenges the ethics of genetic manipulation and cloning. "Shocking and thought-provoking...Cook's best to date." (ssociated Press) |
 |
The Calcutta Chromosome: A Novel of Fevers, Delirium & Discovery by Amitav Ghosh (Author) From Victorian lndia to near-future New York, The Calcutta Chromosome takes readers on a wondrous journey through time as a computer programmer trapped in a mind-numbing job hits upon a curious item that will forever change his life. When Antar discovers the battered I.D. card of a long-lost acquaintance, he is suddenly drawn into a spellbinding adventure across centuries and around the globe, into the strange life of L. Murugan, a man obsessed with the medical history of malaria, and into a magnificently complex world where conspiracy hangs in the air like mosquitoes on a summer night. |
 |
Chromosome Abnormalities and Genetic Counseling (Oxford Monographs on Medical Genetics, No. 46) by R. J. McKinlay Gardner (Author), Grant R. Sutherland (Author) Genetic Health Services Victoria and Murdoch Children's Institute, Melbourne, Australia. Discusses genetic counseling and how to help concerned parents make informed decisions. Covers the basics of genetics, parents with chromosomal abnormality, and prenatal diagnosis. Previous edition: c1996. |
 |
Neon Genesis Evangelion: Angel Chromosome XX Series A-14 Zurzel-XX by Yamato Neon Genesis Evangelion: Angel Chromosome XX Series A-14 Zurzel-XX. |
 |
His & Hers Chromosome Towels - XX by T.R. Miller Co., Inc. Geeks understand the importance of towels. And sometimes two geeks get together and live in the same house. Know what that leads to? Towel fights. Not the sort where you wet one end and snap it, but fights over whose towel is whose. First, we thought we'd solve that the same way nations do. But it's impractical to stick flags in towels. They never stay upright, and then the nylon gets all wet, and it's just a bad scene all around. So we went with the monogram option. Choose your towel by the applicable set of sex chromosomes. And voila! No more towel confusion. We're afraid if you live in a single sex dorm, this isn't going to help. Unless you're the only science-y one there. And then, score! |
 |
As An Ex-Anorexic's Six Sick Ex It A Faulty Chromosome (Primary Contributor) |
 |
Chromosomes & Genes Starring: Sunburst Visual Media Directed By: Sunburst Visual Media Modern society is being bombarded with new information about genetics every day! Make sure your students understand the key concepts that will enable them to fully understand this topic. Students are intrigued that genes can influence looks and behavior! |
 |
The X in Sex: How the X Chromosome Controls Our Lives by David Bainbridge (Author) "A tiny scrap of genetic information determines our sex; it also consigns many of us to a life of disease, directs or disrupts the everyday working of our bodies, and forces women to live as genetic chimeras. The culprit--so necessary and yet the source of such upheaval--is the X chromosome, and this is its story. An enlightening and entertaining tour of the cultural and natural history of this intriguing member of the genome, The X in Sex traces the journey toward our current understanding of the nature of X. From its chance discovery in the nineteenth century to the promise and implications of ongoing research, David Bainbridge shows how the X evolved and where it and its counterpart Y are going, how it helps assign developing human babies their sex--and maybe even their sexuality--and... |
 |
Chromosome Gun by Ultralyd |
|
Chromosomes & Genes (Teacher's Video Company) |
| © 2009 BrightSurf.com |