Citation:Griswold,A(2008)Genome packaging in prokaryotes: the circular chromosome of E colireservationforsixcom Education1(1):57 How do bacteria, lacking a nucleus, organize and pack their genome into the cell? Supercoiling enables this but forces a different kind of transcription and translation in prokaryotes Most students learnat an early age that organisms can be broadly divided into two types: prokaryotesand eukaryotes In primary school, children are taught that the main differencebetween these organisms is that eukaryotic cells contain membrane-boundorganelles, such as the nucleus, while prokaryotic cells do not There is muchmore to the story, however, particularly with regard to chromosomal structureand organization Much of what isknown about prokaryotic chromosome structure was derived from studies of Escherichia coli, a bacterium that livesin the human colon and is commonly used in laboratory cloning experiments Inthe 1950s and 1960s, this bacterium became the model organism of choice for prokaryoticresearch when a group of scientists used phase-contrast microscopy andautoradiography to show that the essential genes of E coli are encoded on a single circular chromosome packaged withinthe cell nucleoid (Mason & Powelson, 1956; Cairns, 1963) Prokaryotic cells donot contain nuclei or other membrane-bound organelles In fact, the word "prokaryote"literally means "before the nucleus" The nucleoid is simply the area of aprokaryotic cell in which the chromosomal DNA is located This arrangement isnot as simple as it sounds, however, especially considering that the E coli chromosome is several orders ofmagnitude larger than the cell itself So, if bacterial chromosomes are sohuge, how can they fit comfortably inside a cell—much less in one small cornerof the cell? The answer to this question lies in DNA packaging Whereas eukaryotes wrap their DNA around proteins called histones to help package the DNA into smaller spaces, most prokaryotes do not have histones (with the exception of those species in the domain Archaea) Thus, one way prokaryotes compress their DNA into smaller spaces is through supercoiling (Figure 1) Imagine twisting a rubber band so that it forms tiny coils Now twist it even further, so that the original coils fold over one another and form a condensed ball When this type of twisting happens to a bacterial genome, it is known as supercoiling Genomes can be negatively supercoiled, meaning that the DNA is twisted in the opposite direction of the double helix, or positively supercoiled, meaning that the DNA is twisted in the same direction as the double helix Most bacterial genomes are negatively supercoiled during normal growth E coli", "true", "Figure 1", "Supercoiled chromosome of E coli", "", "All rights reserved", "623", "900", "");"> E coli", "true", "Figure 1", "Supercoiled chromosome of E coli", "", "All rights reserved", "623", "900", "");">Figure 1 During the 1980s and1990s, researchers discovered that multiple proteins act together to fold andcondense prokaryotic DNA In particular, one protein called HU, which is themost abundant protein in the nucleoid, works with an enzyme called topoisomeraseI to bind DNA and introduce sharp bends in the chromosome, generating thetension necessary for negative supercoiling Recent studies have also shownthat other proteins, including integration host factor (IHF), can bind tospecific sequences within the genome and introduce additional bends (Rice et al, 1996) The folded DNA is thenorganized into a variety of conformations (Sinden & Pettijohn, 1981) thatare supercoiled and wound around tetramers of the HU protein, much likeeukaryotic chromosomes are wrapped around histones (Murphy & Zimmerman,1997) Once the prokaryoticgenome has been condensed, DNA topoisomerase I, DNA gyrase, and other proteinshelp maintain the supercoils One of these maintenance proteins, H-NS, plays anactive role in transcription by modulating the expression of the genes involvedin the response to environmental stimuli Another maintenance protein, factorfor inversion stimulation (FIS), is abundant during exponential growth andregulates the expression of more than 231 genes, including DNA topoisomerase I(Bradley et al, 2007) Supercoilingexplains how chromosomes fit into a small corner of the cell, but how do theproteins involved in replication and transcription access the thousands ofgenes in prokaryotic chromosomes when everything is packaged together sotightly? It has been determined that prokaryotic DNA replication occurs at arate of 1,000 nucleotides per second, and prokaryotic transcription occurs at arate of about 40 nucleotides per second (Lewin, 2007), so bacteria must havehighly efficient methods of accessing their DNA strands But how? Researchers havenoted that the nucleoid usually appears as an irregularly shaped mass withinthe prokaryotic cell, but it becomes spherical when the cell is treated withchemicals to inhibit transcription or translation Moreover, duringtranscription, small regions of the chromosome can be seen to project from thenucleoid into the cytoplasm (i, inside the cell), in which they are connected to ribosome and allows easy access via different code transcription proteins (Dürrenberger et al In the process of positive development in the process of inhibition to explain, however, transcription, the projections are removed in the form of Teulad and forming the spherical shape mentioned above, because there is a nuclear membrane, The cell period in the standard organism, transcription must be used in the nature before RNA to be synthesized. "," 881 "," 677 "," ");" ");" Figure 2: Hirsch -CHICK IXODES SP) carrying bacteria (Borrelia sp), Borreliosis Lyme, "true", "Some rights are reserved", ",,", "," 881 "," 677 "," ") ; This black leg) has recently caused Borrelia SP (Borrelia SP) that has caused Lyme -Borreliais. It is clear that the only size is not everything in the relationship, containing a single round DNA molecule, forming a single round, forming The genome of their recent studies contains certain prokaryotes are four linear or circular chromosomes; Other like Bacillus Subtilis, Fornucloids, very similar to school, but you see some architectural proteins to do this, Archea -Dna -Molecules, using some architectural proteins, ARCAEA -DNA -DNA - Molecules, but using some architectural proteins, Archaea -dnna molecules, you use it, ADNA matrix. A sorting field including non -unicers Prokaryote, can share many points Similar to biology Grace, overlapping a profit was overlooked.
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It is important to consider more architectural proteins rather than architectural proteins instead of architectural proteins described, the DNA complex of the standard creature (minsky et al., 1997) Available, it will be easier to create mutations in laboratory studies. Add -tromosome is linear or circle)))))))))) For example, Borrelia contains plasmids of round and linear bruises, which are forcing ticks and humans to be responsible for humans (Fraser et al., 1997), usually much smaller and independent of restricting repair Treatment of genes that certain plasmids in cells in cells in chromosomes or % of mobile devices of genetic devices under the standard organism, in addition, are in contrast to the standard chromosome. , most genome propiots are organized in poleric groups or more than a coding area linked to a promotional and is separated by just a few pairs of facilities, found in poleric. The proteins encoded by each opera have been hired into a single task, such as: B.
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The metabolism of the sugar in products can be used for energy (Figure 3) . The structural code gene for protein code is related to lactose imports and metabolism in bacteria. The three structural genes are encoded for proteins related to the import of milk sugar and metabolism in bacteria. The genes are organized in a cluster called Lake Oper "," 627 "," http: // wwwrevationForsixcom/ReservationFationFationforsixcom_eduction "," Operon Lac in bacteria in bacteria in harmony with bacteria in bacteria.
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A bacterium consists of taking a bacterium. Promotionists, operators and three structural genes of these areas appear in a certain agreement before NT and the diagram shows the operon from left to right. The following areas are displayed: First, red stimulants, then yellow mathematics and finally three structural genes, of which Beta Galactosidase is included in the blue color of beta -galacosa in Additional regulatory chains of the orange on the left of the promotional house in the area, upstream of clarity) "=" InlinLinks "> Details of Figure Procariota -DNA organization, therefore, unlike Eukaryote by according to Some of the important ways. The condensation process that Nacoeid Dalas on a super DNA roll and the combination of different architectural proteins, because DNA P Rolarote can interact with cytoplasm, transcription and Translation at the same time.
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Each one of each of the standard biological DNA contains some linear chromosomes in the chromosomes of the Biological Biology. The stars of each gene (meaning diploid) a number of standard human biological genes are held in opera, but most are not a disease: climbing up Com 439, 524 from 525 (2006) Doi: 101038 / 439524A (link to the article) Ahner, S E, et al. How many DNA encodes the Biological Biology? Theoretical Biology Magazine 252, 587 from 592 (2008) Bendich, to J&DRLICA, K -Cromosoms Prokaryote and Eukaryote: What is the difference? Bioessays 22, 481 from 486 (2000) of GENSE of Escherichia Coli in some stages of growth microorganisms 153, 292-2940 (2007) Dürrenberger, M, et al. 4757 from 1768 (1988) Endy, D and Brent, R, modify the reserve of behavioral acts of the size of the size of a Megab facility in Borrelia Burgdorferi bacteria, archive documents of Lyme Disease Disease.
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The National Academy of Science 86, 5969 Story5973 (1989) -Spirchochete, Borrelia Burgdorferi reserves reserves reserves 390, 580, 580, 580, 580, 580 reserve reserve reserves in here: Escherichia comparison Coli and Framper, B Gen IX (Sudbury, Ma, Jones and Bartlett, 200 7) Mason, D J and Powelson, nuclear parts as observed a new technology for a new technology.