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In eukaryotes DNA replication proceeds in one direction down the DNA molecule?
Wiki User
∙ 11y ago
DNA contains the map of how the cell runs and survives. Replication is needed when a cell has to replace itself or another cell. This provides a way for cells to renew itself. Each strand of DNA needs to be copied and added to the new cell that is being created.
During replication, the nitrogenous bases separate and allow replication to happen. This the process.
1. Helicase is added to the DNA strand to separate the strands. It causes the nitrogenous bases to break apart and create a replication bubble. At the end of the bubble, there are replication forks that cause elongation of the DNA strands. Proteins prevent the strands from re-sticking.
2. DNA polymerase is used for process of adding new new nitrogenous bases to the separated strands. It starts at an origin of replication and moves in a direction from the 3' side of the strand to the 5' side. It can only add nucleotides in this direction. The strand that is synthesized continuously in this direction is known as the leading strand.
3. Replication moves in the same direction on both strands. It does not encounter much resistance on the leading strand which has the direction of 3' to 5'. The other strand has an anti-parallel direction to the leading strand it is complementary and runs in 5' to 3'. This is known as the lagging strand. This strand needs RNA primer to start the replication process. After the RNA primer starts the process, DNA polymerase starts adding the DNA nucleotides. This can only happen in small segments and is known as Okazaki segments. RNA primer is used for each segment to continue the replication process. After each segment is done, DNA polymerase removes the RNA primer segments and replaces them with DNA nucleotides. Ligase glues the different DNA segments together to create a continuous strand.
4. The end of the strands cannot be replicated and are left out of the replication. This area is referred to as telomeres and do not contain genetic material. The loss of this information does not change the expression of the genes.
5. During the synthesis, DNA polymerases scan the strands and makes sure that nucleotides are correctly matched. If there is an incorrectly matched nucleotide, enzymes fix the problem by replacing the nucleotide. Mutations within the DNA sequence are rare because of this proofreading. 6. After this process there are 2 complete strands of the same DNA.
7. If there is damage to DNA sequence it can be repaired through a process called nucleotide excision repair. Nuclease cuts out the incorrect matching and then replaces it with the correct DNA. Ligase then glues the strand back together. Damage can come from chemical or motor damage.
Wiki User
∙ 14y ago
Wiki User
∙ 11y agoYes. Everything is made from 5' to 3'. Of course, since the two strands are antiparallel to each other, the template will be read from 3' to 5' even though the replication itself is done from 5' to 3'.
Wiki User
∙ 15y agoIf your are talking about on a cellular or molecular level, DNA always occurs from a 5 to 3 direction. Ethically, I don't know human cloning possibly?
Wiki User
∙ 11y agoYes, I believe from 5' (read:five prime) to 3'. I can't remember how to identify which end is which, sorry.
Wiki User
∙ 10y agoFALSE
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True or false replication start at one end of DNA molecule and proceeds to the other end?
False: DNA replication starts at origins of replication which can be anywhere on the DNA molecule. Replication is taking place at multiple origins at the same time.
Transcription proceeds when RNA polymerase?
Attaches to a promoter molecule.
How do eukaryotes speed the process of replication-since they have multiple long chromosomes?
The eukaryotic genome is so much larger than the prokaryotic genome that it would not be practical to rely on a single origin of replication site when copying it for cell division. By incorporating several, the eukaryotic cell can divide without unnecessarily long delay in chromosomal replication.
Transcription is the process of what?
separates the DNA strand and making a complimentary strand
How does the original strand of DNA relate to the two new DNA molecules after replication?
Well, if you envision a DNA strand how it is formatted it might be a little easier to understand.Think of it like this:(Letters represent nucleotides; Adenine, Guanine, Thymine, Cytosine)A--------TT--------AC--------GG--------CIn DNA transcription the two sides of our strand split and attaches new complimentary base pairs. So when DNA replicates the first step would look like this:A---- ----TT---- ----AC---- ----GG---- ----CNext, new complimentary base pairs attach to the split strands.A----T A----TT----A T----AC----G C----GG----C G----CSo as you can see the replication creates identical copies. The only variation arises when the DNA is involved in some sort of DNA mutation.This is a very simplified example of DNA replication. In real replication the strands are millions of nucleotides long, making the chance of mutation extremely likely.To sum up, the two replicated DNA strands will be nearly identical to the original DNA strand.
True or false replication start at one end of DNA molecule and proceeds to the other end?
False: DNA replication starts at origins of replication which can be anywhere on the DNA molecule. Replication is taking place at multiple origins at the same time.
True or false In eukaryotic chromosomes DNA replication begins at a single point in the chromosome and proceeds in two direction?
It's true, it's in the book
Does DNA replication start at only one place in the DNA?
What do you mean by one area? If by one area you mean does it start at one area then stop and continue on another area then no, DNA replication is continuous and when it takes place it is the most important thing going on in the cell. The cells resources are directed at this process * DNA replication means copying the entire DNA molecule, so it involves the entire molecule, but not all at the same time. In bacteria (prokaryotic cells) replication begins at one point in the molecule and continues all the way round the circular molecule.Beginning at just one place would take too long in eukaryotic cells; someone has calculated that our longest chromosomes would take about a fortnight to replicate, and we cannot wait that long! So replication begins at a number of sites along the length of the DNA molecule. At each replication site, as the DNA strands are separated there is a bulge in the molecule called a replication bubble. As replication proceeds these bubbles become longer, and eventually they merge into one another and the job is done.
What are the basic differences between prokaryic and eukaryotic?
Prokaryotes do not have a nuclear membrane or nucleoli, Eukaryotes do. Prokaryote have no organells, Eukaryote do. Prokaryotes usually have a single circular chromosome lacking histones. Eukaryotes have multiple linear chromosomes with histones. Prokaryotes replicate by binary fission, Eukaryotes by mitosis and meiosis.
Transcription proceeds when RNA polymerase?
Attaches to a promoter molecule.
How do eukaryotes speed the process of replication-since they have multiple long chromosomes?
The eukaryotic genome is so much larger than the prokaryotic genome that it would not be practical to rely on a single origin of replication site when copying it for cell division. By incorporating several, the eukaryotic cell can divide without unnecessarily long delay in chromosomal replication.
What serves as the template for DNA replication?
The eukaryotic chromosomes are larger in size. Hence in order to overcome the limitation of DNA synthesis, multiple origins of replication are present in order to complete replication in a reasonable period of time.At the replication origin the strands of DNA must dissociate and unwind in order to allow access to DNA polymerase.Unwinding of the duplex at the origin as well as along the strands as the replication process proceeds is carried out by helicases.The resultant regions of single-stranded DNA are stabilized by the binding of single-strand binding proteins.The stabilized single-stranded regions are then accessible to the activities of other enzymes required for replication to proceed.The site of the unwound template strands is termed the replication fork.In order for DNA polymerases to synthesize DNA they must encounter a free 3'-OH which is the substrate for attachment of the 5'-phosphate of the incoming nucleotide.During replication the 3'-OH is supplied through the use of an RNA primer, synthesized by the primase activity. The primase utilizes the DNA strands as templates and synthesizes a short stretch of RNA generating a primer for DNA polymerase.Synthesis of DNA proceeds in the 5'---->3' direction through the attachment of the 5'-phosphate of an incoming deoxy nucleosidetriphosphate (dNTP) to the existing 3'-OH in the elongating DNA strands with the concomitant release of pyrophosphate.Initiation of synthesis, at origins of replication, occurs simultaneously on both strands of DNA.DNA synthesis process then proceeds bidirectionally, with one strand in each direction being copied continuously and one strand in each direction being copied discontinuously.The experimental support for this bidirectional mode of replication in the cells of higher eukaryotes was acquired by the fiber autoradiography of labeled DNAs got from mammalian cell cultures. When the replicating DNA extracted and isolated from eukaryotic cells are examined under the electron microscope, the clear "bubble" like structures extending from multiple replication origins are clearly visible.source: www.examville.com
Transcription is the process of what?
separates the DNA strand and making a complimentary strand
What is the plural form for word proceeds?
The noun 'proceeds' is a plural, uncountable(mass) noun; a type of aggregate noun, a word an indefinite number of elements or parts.The noun 'proceeds' is a word for an amount of money derived from a commercial or fund-raising venture.The word 'proceed' is a verb (proceed, proceeds, proceeding, proceeded), meaning to to go in a particular direction, or to continue to happen.
What are genetic mutation and natural selection?
Together, genetic mutation and natural selection determine in what 'direction' evolution proceeds.
The meaning of anti clockwise?
The word anticlockwise, can be seen from the prefix anti which literally means against.For example in a clock a clockwise direction moves or proceeds to the same direction for example in trigonometric ratios or the wall clock. This means anti clock wise is proceeding to the direction or the opposite direction.
What are the elements of DNA polymerase?
DNA polymerase III (not DNA polymerase) is an enzyme that works in association with other enzymes during the replication of a DNA molecule. DNA replication begins when the enzyme, known as helicase unwinds a DNA strand. Helicase unwinds a DNA strand, thus, in the process, separating the two DNA templates. The result of the unwinding of the DNA molecule is the formation of a replication bubble. Once a DNA molecule is unwound, it is not stable. The DNA molecule is untwisted, broken and rearranged by an enzyme called topoisomerase in order to create stability at the ends of a replication bubble. In addition, the DNA replication bubble is further stabilized by a group of protein complexes known as single strand binding proteins.Once the DNA molecule is unwound and stabilized, an enzyme called primase assembles an RNA sequence that is complementary to the adjacent DNA template. The purpose of this initial RNA sequence is to provide a point at which DNA polymerase III can start to add nucleotides to the corresponding DNA template. Unlike RNA polymerase, DNA polymerase III requires an RNA sequence, which is known as a primer. DNA polymerase III can attach a nucleotide only to the 3 prime end of an existing nucleotide sequence. Once a primer is assembled by primase, DNA polymerase III begins its work of adding nucleotides to the 3 prime end of the primer.It is important to note that replication proceeds in two directions, since a DNA replication bubble consists of two DNA templates. Since DNA polymerase III proceeds in the three prime to 5 prime direction at one DNA template, it also has to proceed in the 3 prime to 5 prime direction on the other DNA template. Since the template run in opposite directions, the second template will consist of multiple primers and thus short segments of DNA. These short segments of DNA are known as Okazaki fragments. The Okazaki fragments are created by DNA polymerase three since it is only able to proceed in the 3 prime to 5 prime direction.After DNA polymerase III completes its work, DNA polymerase I begins to replace the RNA nucleotides of the primers with DNA nucleotides. Once DNA polymerase I replaces the RNA nucleotides with DNA nucleotides, DNA ligase joins the Okazaki fragments together and the result is a new DNA template.
