In biology, epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence. The Greek prefix epi- in epigenetics implies features that are "on top of" or "in addition to" the traditional genetic basis for inheritance. Epigenetics most involves changes that affect gene activity and expression, but the term can be used to describe any heritable phenotypic change; such effects on cellular and physiological phenotypic traits may result from external or environmental factors, or be part of normal development. The standard definition of epigenetics requires these alterations to be heritable in the progeny of either cells or organisms; the term refers to the changes themselves: functionally relevant changes to the genome that do not involve a change in the nucleotide sequence. Examples of mechanisms that produce such changes are DNA methylation and histone modification, each of which alters how genes are expressed without altering the underlying DNA sequence.
Gene expression can be controlled through the action of repressor proteins that attach to silencer regions of the DNA. These epigenetic changes may last through cell divisions for the duration of the cell's life, may last for multiple generations though they do not involve changes in the underlying DNA sequence of the organism. One example of an epigenetic change in eukaryotic biology is the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become differentiated cells. In other words, as a single fertilized egg cell – the zygote – continues to divide, the resulting daughter cells change into all the different cell types in an organism, including neurons, muscle cells, endothelium of blood vessels, etc. by activating some genes while inhibiting the expression of others. Some phenomena not heritable have been described as epigenetic. For example, the term "epigenetic" has been used to describe any modification of chromosomal regions histone modifications, whether or not these changes are heritable or associated with a phenotype.
The consensus definition now requires a trait to be heritable. The term epigenetics in its contemporary usage emerged in the 1990s, but for some years has been used with somewhat variable meanings. A consensus definition of the concept of epigenetic trait as a "stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence" was formulated at a Cold Spring Harbor meeting in 2008, although alternate definitions that include non-heritable traits are still being used; the term epigenesis has a generic meaning of "extra growth", has been used in English since the 17th century. From the generic meaning, the associated adjective epigenetic, British embryologist C. H. Waddington coined the term epigenetics in 1942 as pertaining to epigenesis, in parallel to Valentin Haecker's'phenogenetics'. Epigenesis in the context of the biology of that period referred to the differentiation of cells from their initial totipotent state during embryonic development; when Waddington coined the term, the physical nature of genes and their role in heredity was not known.
He used it instead as a conceptual model of how genetic components might interact with their surroundings to produce a phenotype. Waddington held that cell fates were established during development in a process he called canalisation much as a marble rolls down to the point of lowest local elevation. Waddington suggested visualising increasing irreversibility of cell type differentiation as ridges rising between the valleys where the marbles are travelling. In recent times, Waddington's notion of the epigenetic landscape has been rigorously formalized in the context of the systems dynamics state approach to the study of cell-fate. Cell-fate determination is predicted to exhibit certain dynamics, such as attractor-convergence or oscillatory. Robin Holliday defined epigenetics as "the study of the mechanisms of temporal and spatial control of gene activity during the development of complex organisms." Thus, in its broadest sense, epigenetic can be used to describe anything other than DNA sequence that influences the development of an organism.
More recent usage of the word in biology follows stricter definitions. It is, as defined by Arthur Riggs and colleagues, "the study of mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence."The term has been used, however, to describe processes which have not been demonstrated to be heritable, such as some forms of histone modification. For example, Adrian Bird defined epigenetics as "the structural adaptation of chromosomal regions so as to register, signal or perpetuate altered activity states." This definition would be inclusive of transient modifications associated with DNA repair or cell-cycle phases as well as stable changes maintained across multiple cell generations, but exclude others such as templating of membrane architecture and prions unless they impinge on chromosome function. Such redefinitions however are still subject to debate; the NIH "Roadmap Epigenomics Project", ongoing as of 2016, uses the following definition: "For purposes of this program
Marcin Białobłocki is a Polish cyclist competing for British amateur team Steele Davis Via Roma RT. He has competed professionally for British teams between 2011 and 2017, he rejoined the Velosure team for the 2014 season, after his previous team – Team UK Youth – folded at the end of the 2013 season. In December 2014 he was announced as part of the inaugural squad for the ONE Pro Cycling team for the 2015 season, he took part in the 2015 Tour de Pologne as a member of the Polish national team, where he won the race's final stage time trial. UK Time Trials Marcin became a well known name in the UK time trialling community riding for One Pro Cycling when he took the 10 mile competition record from Alex Dowsett, with 16-36, he went on to take Dowsett’s 25 mile comp record with a time of 44-04. This time was improved on in 2018 when Marcin did a ride of 42-58 on the R25/3H course in Wales. In 2018 Marcin took the 50 mile comp record with a time of 1-30-31, three minutes faster than the previous record set only weeks before.
He joined the Polish team CCC–Sprandi–Polkowice in 2017, having ridden the previous two seasons for British team ONE Pro Cycling. He was named in the start list for the 2017 Giro d'Italia. Media related to Marcin Białobłocki at Wikimedia Commons Marcin Białobłocki at ProCyclingStats
Kate Eliana Valdez Sisante, professionally known as Kate Valdez, is a Filipina actress and model. She is working as an exclusive artist of GMA Network, is known for her role as Violet in Destiny Rose, as Mira in Encantadia, she plays as Natalie/Rosemarie in Onanay. Kate Valdez, whose real name was Kate Eliana Sisante, was born in the Philippines to Edmond and Teresita Sisante, she has a sister named Karen Ashley. Valdez is enrolled in a private school in Cavite. Valdez started modeling while still in elementary school and subsequently joined amateur beauty pageants. Valdez discovered her knack for acting. In 2015, Valdez signed a contract with GMA Artist Center. Valdez appeared on Destiny Rose as Violet Vitto Jacobs. In 2016, Valdez became a part the 2016 requel-sequel of Encantadia as Mira portrayed by Yasmien Kurdi; the character is the daughter of Pirena, played by Glaiza de Castro, was portrayed by Sunshine Dizon in the original series. Valdez has appeared in other programs on GMA Network and is a TV commercial model for various local labels.
Gregory Kirk "Greg" Ridgeway is associate professor of criminology and statistics at the University of Pennsylvania, where he is the director of the M. S. program in criminology. Ridgeway received his B. S. from California Polytechnic State University in 1995 and his M. S. and Ph. D. from the University of Washington in 1997 and 1999, respectively. All three of his degrees are in statistics, his Ph. D. thesis was entitled "Generalization of boosting algorithms and applications of Bayesian inference for massive datasets". Early in his career, Ridgeway worked at the RAND Corporation, where he served as the director of the Safety and Justice Program from 2009 to 2012, of the Center for Quality Policing from 2008 to 2012, he served as the acting director of the National Institute of Justice for 19 months before joining the University of Pennsylvania in August 2014. Ridgeway's research focuses on using statistical techniques to examine aspects of the United States' criminal justice system; these aspects include, but are not limited to, stop-and-frisk in New York City, which, in a 2007 study, he found was racially biased, with blacks and Hispanics being more to be frisked, searched, or arrested once stopped.
Spiroplasma phage 1-R8A2B is a filamentous bacteriophage in the genus Plectrovirus of the family Inoviridae, part of the group of single-stranded DNA viruses. The virus has many synonyms, such as SpV1-R8A2 B, Spiroplasma phage 1, Spiroplasma virus 1, SpV1. SpV1-R8A2 B infects Spiroplasma citri, its host itself is a prokaryotic pathogen for citrus plants. The phage is a spiroplasmal virus of morphologic group 1, isolated from Spiroplasma citri strain R8A2 subclone B. SpV1 viruses are classified by their naked rods. SpV1 virus-like particles were observed by electron microscopy in 1973 during the first ultrastructural characterization of S. citri. Nearly two decades in 1990, the specific strain of SpV1-R8A2 B was first reported in the publication of its complete nucleotide sequence of its genome; the prefixes for the family and genus are both derived from Greek: Ino is from nos, meaning "muscle filament," and Plectro is from plektron, meaning "small stick." Group 1 spiroplasmal viruses are long, non-enveloped, filamentous particles containing a circular, ssDNA molecule of around 8 kilobases.
The rods are nearly straight with one rounded end and one more variable end. Their lengths are about 300 nm or less and their diameters are about 15 nm with 4 ± 2 nm hollow cores, they lack lipids. SpV1-R8A2 B's complete genome contains 8273 nucleotides totaling 37.1% A, 8.1% C, 14.8% G, 40% T. It has 22.9% GC-content. Altogether, the phage has 12 genes. Virions of SpV1 are sensitive to ether, they are resistant to cold and heat, a wide range of pH, non-ionic detergents. SpV1 buoyant densities are 1.21 g/cm3 in metrizamide. Spiroplasma phages affect members of the genus Spiroplasma, which are part of the class Mollicutes, a group of small bacteria without cell walls. In particular, SpV1-R8A2 B infects S. citri found on the Morocco strain. S. citri is the causative agent of Citrus stubborn disease on plants of the genus Citrus. There is a high frequency of SpV1 natural infection found in Spiroplasma strains. An early electron microscopic study of negatively stained preparations revealed SpV1 particles in 38 of 67 Spiroplasma strains examined.
A single virus particle is sufficient enough to infect a host cell. Infection is nonlytic; the S. citri chromosome contains CDS of plectrovirus prophages at multiple sites truncated, many homologous to SpV1. There is evidence that shows, in the sequenced S. citri genome, at least 20.5% of CDS are phage-related, while 47.2% of CDS are of unknown function. These sequences of unknown function could be remnants of viral sequence insertions, a common feature with other Mollicute genomes, as they contain repeated clusters of genes that could be "mobile genetic elements or remnants of ancient phage attacks." Insertion of the viral sequences occurs by encoded putative transposases resembling those of insertion elements. Integration of a plectrovirus genome can occur upon viral infection. Resistance has been shown to occur with subsequent infection. Insertion sequence elements may have resulted in gene disruptions, genome rearrangements, genome expansions; as a Plectrovirus, the phage's entry mechanism is adsorption to membrane-bound cellular receptors.
Transcription takes place in the cytoplasm with a cellular enzyme transcriptase. Genome replication occurs within the cellular membrane in the cytoplasm. Host cell DNA-dependent DNA polymerase serves as the replicase, replication occurs by rolling circle. Virion assembly takes place in the cellular membrane; the phage's exit mechanism is by extrusion. The typical replication cycle of Inoviridae: Viral g3p protein mediates pilus-mediated adsorption of the virus onto host cell. Pilus retraction pulls the virion to the host internal membrane; the proteins of the capsid mediate the injection of the viral DNA through bacterial membranes into cell cytoplasm. Host polymerase convert the ssDNA viral genome into a covalently closed dsDNA called replicative form DNA. dsDNA transcription by host RNA polymerase gives rise to viral mRNAs. Viral g2p protein nicks RF DNA strand at the origin of replication. Strand replication occurs by rolling circle. New ssDNA genomes are converted into new RF molecules, further transcription occurs.
When enough g5p protein is synthesized, conversion into RF dsDNA is inhibited, as neo-synthesized genomic ssDNA is covered with g5p. G5p are replaced by g8p proteins to trigger the assembly of the viral capsid. New virions are secreted from host cell. Infected cells continue to produce virions indefinitely; the replicative form of SpV1 has been attempted to be used as a vector to express foreign genes in S. citri R8A2. The goal is to allow foreign genes to be transcribed, translated into proteins, maintained in a stable form for generations. However, the recombinant viral DNA can prove to be unstable after passaging. SpV1-R8A2 B can be isolated from its host; the replicative form can be cloned in E. coli. Purification before culturing can be accomplished by CsCl density gradient centrifugation. UniProt: Gene ontology for Spiroplasma virus SpV1-R8A2 B NCBI: Spiroplasma phage 1-R8A2B, complete genome
CNN Arabic is a news website located in Dubai launched on 19 January 2002. Part of the CNN network, it provides international news in the Arabic language, with continuous updates on regional and international developments; the CNN Arabic website is managed by a number of professional and experienced Arab journalists. The website consists of a number of sections, including world news, Middle East and technology, business and sports, in addition to special reports and videos; the website provides a number of additional services such as a free email feed of breaking news, breaking news via SMS. The website includes information about CNN network and advertising on television and the different websites. During the 2019 constitutional referendum in Egypt which would extend the presidential terms limit, CNN Arabic started a poll allowing people to vote whether they endorse or oppose the referendum. According to Amr Waked, an Egyptian actor and a political dissident, the votes in the CNN Arabic poll was going normal until 14:42 to 14:57 the poll results changed.
He accused the CNN Arabic of manipulating the poll results in favour of the Egyptian president el-Sisi. official website