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Centromeres cross over, a lot
June 13, 2008Recombination at centromeres is higher than anywhere else on the chromosome, even though methyltransferases do their best to prevent it, say Jaco et al., as published in the June 16 issue of the Journal of Cell Biology.
Centromeric recombination has been hard to study because the DNA at centromeres is so repetitive-it's hard to see when a segment has switched chromatids. Jaco et al. have now addressed this challenge by using CO-FISH (chromosome orientation fluorescence in situ hybridization). After replication, the two new strands are digested away, leaving the two old strands. Because the strands are complementary in sequence, they can be tagged with strand-specific fluorescent probes. Using just one probe, only one chromatid would show a signal if no recombination had occurred.
Instead, the authors found that both chromatids fluoresced. And not just at one point-on average, the authors counted, centromeres had undergone 15 recombination events. This is about six times the rate of recombination as that seen for an equal length of telomeric DNA, and 175 times the rate for genomic DNA as a whole.
Telomeric recombination is inhibited by protein complexes called shelterins and by DNA methylation. The centromere has no shelterin, but it is methylated. Knockdown of DNA methyltransferases increased recombination at the centromere by about 50%, and decreased centromere length, possibly because of misalignment between repeated segments during recombination, a common problem with repetitive DNA. How methylation limits recombination, and why centromeres didn't lengthen as well as shorten, are unknown.
Their repetitive structure makes centromeres recombinogenic by nature, and the authors suggest that epigenetic regulation may ensure the continued stability of essential binding regions for proteins that link to the centromere.
Rockefeller University Press
Telomeric recombination is inhibited by protein complexes called shelterins and by DNA methylation. The centromere has no shelterin, but it is methylated. Knockdown of DNA methyltransferases increased recombination at the centromere by about 50%, and decreased centromere length, possibly because of misalignment between repeated segments during recombination, a common problem with repetitive DNA. How methylation limits recombination, and why centromeres didn't lengthen as well as shorten, are unknown.
Their repetitive structure makes centromeres recombinogenic by nature, and the authors suggest that epigenetic regulation may ensure the continued stability of essential binding regions for proteins that link to the centromere.
Rockefeller University Press
Centromeres Current Events and Centromeres 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.
A solution to Darwin's 'mystery of the mysteries' emerges from the dark matter of the genome
Biological species are often defined on the basis of reproductive isolation. Ever since Darwin pointed out his difficulty in explaining why crosses between two species often yield sterile or inviable progeny (for instance, mules emerging from a cross between a horse and a donkey), biologists have struggled with this question.
CSHL researchers explain process by which cells 'hide' potentially dangerous DNA segments
The DNA in the 23 pairs of chromosomes in each of the billions of cells of the human body is so tightly packed that it would measure six feet in length if stretched end to end. A genome of this size can squeeze into a cell's tiny nucleus because it is compressed into highly condensed chromatin fibers by proteins called histones.
CSHL scientists discover link between control of chromosome duplication and segregation
Before a cell can divide into two, first it must duplicate its genetic material--the DNA packed in its chromosomes. The two new sets of chromosomes then have to be separated from one another and correctly distributed to the resulting "daughter" cells, so that both daughter cells are genetically identical to the original, or "parent," cell.
Hotspots found for chromosome gene swapping
Crossovers and double-strand DNA breaks do not occur randomly on yeast chromosomes during meiosis, but are greatly influenced by the proximity of the chromosome's telomere, according to research in the laboratory of Whitehead Fellow Andreas Hochwagen.
Exploring the Dark Matter of the Genome
Not so long ago, the difficult-to-sequence, highly repetitive, gene-poor DNA found in regions of chromosomes known as heterochromatin was called "junk." Like dark matter in the universe, the true nature of heterochromatin was unknown.
Researchers attach genes to minichromosomes in maize
A team of scientists at the University of Missouri-Columbia has discovered a way to create engineered minichromosomes in maize and attach genes to those minichromosomes.
Researchers sequence the basal eukaryote Tetrahymena thermophila
In an effort to improve our understanding of eukaryotic evolution, a team of over 50 researchers led by Jonathan Eisen sequenced the macronuclear genome of the single-celled ciliate Tetrahymena themophila.
Retrovirus Invasion in Primate Evolution; Limiting the Transmission of Rabies: Press Release from PLoS Biology
The Chimp Genome Reveals Retroviral Invasions in Primate Evolution It's been known for a long time that only 2% - 3% of human DNA codes for proteins. Much of the rest of our genomes - often referred to as junk DNA - consists of retroelements, some of which can occasionally replicate and move to a new location in the genome.
HIRA, a new factor in the genome's 3D organizational assembly chain
At the heart of every cell, vital information is "written" on the DNA, a long molecular ribbon almost one meter long bundled inside the nucleus of the cell. For the DNA to fit inside this small space, it is rolled up like a ball of yarn in a highly organized structure called chromatin. Beyond its purely structural role, the spatial organization of DNA is essential to the basic processes of a cell's life because it provides information that is added to that contributed by the genetic code. This ball-like structure, which protects the DNA, plays an important role in all the functions of our genome, most notably in the modulation of the genes' expression. At the Institute Curie, CNRS
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Centromere: An entry from Macmillan Reference USA's Macmillan Reference USA Science Library: Genetics by Joseph G. Gall (Author) This digital document is an article from Macmillan Reference USA Science Library: Genetics, brought to you by Gale®, a part of Cengage Learning, a world leader in e-research and educational publishing for libraries, schools and businesses. The length of the article is 534 words. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser. A comprehensive collection of articles on all aspects of genetics, from Mendel to the decoding of the human genome. Explains the workings of genes and chromosomes, genetic diseases, and biotechnology. Covers the ethical, legal, and social issues connected to genetic science and includes coverage of careers in the field. | |
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Centromeres: Webster's Timeline History, 1930 - 2007 by Icon Group International (Author) Webster's bibliographic and event-based timelines are comprehensive in scope, covering virtually all topics, geographic locations and people. They do so from a linguistic point of view, and in the case of this book, the focus is on "Centromeres," including when used in literature (e.g. all authors that might have Centromeres in their name). As such, this book represents the largest compilation of timeline events associated with Centromeres when it is used in proper noun form. Webster's timelines cover bibliographic citations, patented inventions, as well as non-conventional and alternative meanings which capture ambiguities in usage. These furthermore cover all parts of speech (possessive, institutional usage, geographic usage) and contexts, including pop culture, the arts, social... |
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Messy When You're Not Here Harry Arader (Primary Contributor) |
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The Centromere by K. H. Andy Choo (Author) The centromere is an essential structure on all eukaryotic chromosomes that allows the equipartition of chromosomes during mitotic and meiotic cell divisions. Since its cytogenetic recognition as a constructed part of a chromosome many decades ago, great advances have been made in our understanding of this intriguing structure, especially at the molecular level. This book brings together all available information on the centromere. It covers in detail the DNA and protein components of this structure, and their individual functions, in species as diverse as budding and fission yeasts, nematodes, Drosophila, mice, and humans; newly discovered roles of the centromere in marshalling "passenger" proteins; important emerging concepts such as latest centromeres and epigenetic factors;... |
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Centromeres: Webster's Facts and Phrases by Icon Group (Author) Ever need a fact or quotation on centromeres? Designed for speechwriters, journalists, writers, researchers, students, professors, teachers, historians, academics, scrapbookers, trivia buffs and word lovers, this is the largest book ever created for this single word. It represents a compilation from a variety of sources with a linguistic emphasis on anything relating to the term "centromeres," including non-conventional usage and alternative meanings which capture ambiguities. The entries cover all parts of speech (noun, verb, adverb or adjective usage) as well as use in modern slang, pop culture, social sciences (linguistics, history, geography, economics, sociology, political science), business, computer science, literature, law, medicine, psychology, mathematics, chemistry, physics,... |
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All I Need Is You Harry Arader (Primary Contributor) |
![Mimulus finds centromeres in the driver's seat [An article from: Trends in Ecology & Evolution]](http://ecx.images-amazon.com/images/I/51CSNTMYYTL._SL160_.jpg) |
Mimulus finds centromeres in the driver's seat [An article from: Trends in Ecology & Evolution] by H.S. Malik (Author) This digital document is a journal article from Trends in Ecology & Evolution, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser. Description: Sandler and Novitski first pointed out in 1957 that chromosomes could selfishly exploit meiotic asymmetries to maximize their own transmission, in a process termed 'meiotic drive'. However, since then, only post-meiotic processes of non-Mendelian inheritance have received serious scientific attention in studies of transmission distortion. A recent study by Fishman and Willis puts the focus squarely back on meiotic drive. They found completely biased transmission of a centromere-linked locus from an... |
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Centromere: Structure and Evolution (Progress in Molecular and Subcellular Biology) by Durdica Ugarkovic (Editor) The centromere is a chromosomal locus that regulates the proper pairing and segregation of the chromosomes during cell division. Despite their conserved, essential function, centromeres are characterized by the rapid evolution of both centromeric DNA and proteins. This book presents current views on centromere structure and identity. It deals with the epigenetic concept of centromere establishment and maintenance as well as with the role of DNA and centromeric transcripts in centromere formation and function. Special emphasis is placed on centromere evolution: different evolutionary models are discussed in detail and the latest research on the evolution of new centromeres and neocentromeres is presented. |
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Mr. Bluebird Harry Arader (Primary Contributor) |
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Human artificial chromosomes: An entry from Thomson Gale's Gale Encyclopedia of Science, 3rd ed. by Bryan Cobb (Author) The “Gale Encyclopedia of Science” is written at a level somewhere between the introductory sources and the highly technical texts currently available. This six-volume set covers all major areas of science and engineering, as well as mathematics and the medical and health sciences, while providing a comprehensive overview of current scientific knowledge and technology. Alphabetically arranged entries provide a user-friendly format that makes the broad scope of information easy to access and decipher. Entries typically describe scientific concepts, provide overviews of scientific areas and, in some cases, define terms. |
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