dna replication is accomplished using a technique known as:

A single DNA molecule results indouble helix formationwhen two DNA strands are matched and bonded. E. coli has a single origin of replication (as do most prokaryotes), called oriC, on its one chromosome. Each strand has a sugar-phosphate backbone that is created when the phosphate of one nucleotide binds to the sugar of the next using a covalentphosphodiester bond. ", Biologydictionary.net Editors. If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. Sticky ends and blunt ends. Which enzyme is responsible for removing the RNA primers in newly replicated bacterial DNA? c. convert cDNA into messenger RNA. Properties of DNA polymerases used in PCR. It edits the DNA by proofreading every newly added base. A specific sequence of bases- known as the origin of replication determines where this replication bubble begins. A protein called the sliding clamp holds the DNA polymerase in place as it continues to add nucleotides. This continuously synthesized strand is known as the leading strand. Topoisomerase relieves the tension further down the double helix. In the semiconservative model, parental strands separated and directed the synthesis of a . The primers are removed by the exonuclease activity of DNA polymerase I, and the gaps are filled in. The cut sites are: Blunt-ended fragments can be joined to each other by DNA ligase. As a semiconservative process, the double helix is broken down into two strands, where each strand serves as the template for the newly synthesized strand by matching complementary bases. As the replication fork continues down the double helix in the 3 direction of the template strand, another Okazaki fragment can be created closer to the fork. Let's see how restriction digestion and ligation can be used to insert a gene into a plasmid. The sticky ends of the two fragments stick together by complementary base pairing: Next, we take the gene fragment and the linearized (opened-up) plasmid and combine them along with DNA ligase. This means that cells have a limited number of times that they are able to divide via mitosis before signals are sent to prevent further divisions and DNA damage. Check out this, Do you want to learn more about DNA ligase? Biologydictionary.net, June 01, 2020. https://biologydictionary.net/dna-replication/. Telomerase contains a catalytic part and a built-in RNA template. Legal. The target gene has two, We separately digest (cut) the gene fragment and the plasmid with. Which enzyme breaks the hydrogen bonds holding the two strands of DNA together so that replication can occur? In humans, telomerase is typically active in germ cells and adult stem cells; it is not active in adult somatic cells and may be associated with the aging of these cells. A representative temperature profile for each cycle might look like the following: A typical reaction buffer for PCR would something like: (1) Tm = [(number of A+T residues) x 2 C] + [(number of G+C residues) x 4 C], If the annealing temperature is too high, the primers will not anneal. Telomere replication on the lagging strand is as follows: Telomerase is most commonly active in cell types that divide rapidly, such as with embryonic cells, stem cells, sperm cells, and immune cells. Because both bacterial DNA gyrase and topoisomerase IV are distinct from their eukaryotic counterparts, these enzymes serve as targets for a class of antimicrobial drugs called quinolones. That is true, but for a typical restriction digest of human DNA you will get around a million different bands with a range of different sizes on a gel this just looks like a smear of DNA and is of no use in identifying individuals. Mutations in repair genes may lead to serious consequences like cancer. The sticky ends will only hold them together briefly, and if ligase doesn't connect them during that time, they will go back to floating around and bumping into other pieces of DNA and enzymes in the reaction mix. Prokaryotic cells have a simpler but similar nucleotide excision repair system that only requires three proteins. In DNA cloning, restriction enzymes and DNA ligase are used to insert genes and other pieces of DNA into plasmids. . As synthesis proceeds, the RNA primers are replaced by DNA. 3. Is it the lagging strand or the leading strand that is synthesized in the direction toward the opening of the replication fork? Retrieved from https://biologydictionary.net/dna-replication/. After replication, each DNA has one parental or old strand, and one daughter or new strand. Telomeres are short, repeating segments of DNA that are found at the end of each chromosome and do not contain any coding sequences. DNA polymerase III binds to the primer and moves opposite of telomerase to complete the synthesis of the lagging strand. DNA polymerase III attaches to this primer to synthesize a second Okazaki fragment in the 5-3 direction away from the replication fork. Even without thermal denaturation, the amount of enzyme becomes limiting due to molar target excess in later cycles (i.e. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. The nitrogenous bases in DNA are adenine, guanine, cytosine, and thymine. d. verify that the desired DNA sequence has been amplified. Meanwhile, because eukaryotes have linear DNA, telomeres are needed to ensure genetic information is not lost during replication. Why do restrictive enzymes that do blunt cuts even exist if they are so inefficient? Restriction enzymes and DNA ligase are often used to insert genes and other pieces of DNA into plasmids during DNA cloning. Using its own RNA template, telomerase synthesizes the extending telomere, adding additional bases to the 3 end of the lagging strand. DNA polymerase III moves down the leading strand. Theme 5: How Do We Control Our Fertility? DNA Replication of Extrachromosomal Elements: Plasmids and Viruses. This is accomplished by the process of DNA replication. With both DNA polymerase proofreading and the mismatch repair proteins correcting additional mistakes, there is roughly only one mistake for every 1 billion nucleotides synthesized. { "6.1:_Genetic_Transformation_(using_bacteria_and_the_pGLO_plasmid)" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6.2:_Enzyme_kinetics" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6.3:_Ligand_binding" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6.4:_Restriction_Mapping" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6.5:_Polymerase_Chain_Reaction_(PCR)" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6.6:__Use_of_PC_and_internet_for_biochemical_research" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()" }, { "00:_Front_Matter" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "1:_DNA" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "2:_Bacteria" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "3._Biotechnology_1" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "4._Biotechnology_2" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "5._Lab_Notes_Part_1" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "6._Lab_Notes_Part_2" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()", "zz:_Back_Matter" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass230_0.b__1]()" }, [ "article:topic", "polymerase chain reaction (PCR)", "showtoc:no", "authorname:mblaber" ], https://bio.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fbio.libretexts.org%2FBookshelves%2FBiochemistry%2FSupplemental_Modules_(Biochemistry)%2F6._Lab_Notes_Part_2%2F6.5%253A_Polymerase_Chain_Reaction_(PCR), \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\), 6.6: Use of PC and internet for biochemical research, DNA polymerase catalyzes extension of an oligonucleotide in the, Nucleotides incorporated into the nascent oligonucleotide must be, Although DNA polymerases catalyze extension in the 5', PCR amplification is achieved by using oligonucleotide primers. To copy their nucleic acids, plasmids and viruses frequently use variations on the pattern of DNA replication described for prokaryote genomes. Primers are removed, new DNA nucleotides are put in place of the primers and the backbone is sealed by DNA ligase. DNA replication is highly regulated and requires multiple proteins to run efficiently. How do scientists make sure that the bases of the plasmid are complementary to the bases of the inserted DNA? The separation of the two single strands of DNA creates a 'Y' shape called a replication . An RNA primer is added to the leading strand at complimentary bases by primase. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The largest differences are between the domains of prokaryotes (bacteria and archaea) and eukaryotes (all other plant and animal cells). The two strands of DNA in the double helix must run opposite to each other in an anti-parallel fashion. Eukaryotic DNA is highly supercoiled and packaged, which is facilitated by many proteins, including histones (see Structure and Function of Cellular Genomes). DNA polymerase can then cut out this wrong match and replace it with the correct base. The strand with the Okazaki fragments is known as the lagging strand, and its synthesis is said to be discontinuous. DNA polymerases are the enzymes that build DNA in cells. what would happen if the gap never closes? This allowed initially added enzyme to survive temperature cycles approaching 100 C. How does the origin of replication differ between eukaryotes and prokaryotes? DNA pol III adds deoxyribonucleotides each complementary to a nucleotide on the template strand, one by one to the 3-OH group of the growing DNA chain. Many restriction enzymes make staggered cuts, producing ends with single-stranded DNA overhangs. The primer is five to 10 nucleotides long and complementary to the parental or template DNA. This page titled 6.5: Polymerase Chain Reaction (PCR) is shared under a not declared license and was authored, remixed, and/or curated by Michael Blaber. What polymerase enzymes are responsible for DNA synthesis during eukaryotic replication? RNA primase then synthesizes a primer to initiate DNA replication at the single-stranded origin (sso) site of the single-stranded DNA (ssDNA) molecule, resulting in a double-stranded DNA (dsDNA) molecule identical to the other circular DNA molecule. What would have been the conclusion of Meselson and Stahls experiment if, after the first generation, they had found two bands of DNA? The other strand, complementary to the 5 to 3 parental DNA, grows away from the replication fork, so the polymerase must move back toward the replication fork to begin adding bases to a new primer, again in the direction away from the replication fork. The efficiency of ligation and transformation tends to decrease with extremely large inserts. Recall that eukaryotic DNA is bound to proteins known as histones to form structures called nucleosomes. Many restriction enzymes make staggered cuts at or near their recognition sites, producing ends with a single-stranded overhang. These steps produce small DNA sequence fragments known as Okazaki fragments, each separated by RNA primer. The matching of free nucleotides to the parental strands is accomplished by an enzyme called. DNA consists of nucleotides that contain a phosphate backbone, a deoxyribose sugar, and one of four nitrogen-containing bases (adenine [A . In order for DNA polymerase to do this, it must read the template strand from 3-5. This segment cannot be left unattended. Inverted repeat sequences should be avoided so as to prevent formation of secondary structure in the primer, which would prevent hybridization to template, Sequences complementary to other primers used in the PCR should be avoid so as to prevent hybridization between primers (particularly important for the, If possible the 3' end of the primer should be rich in G, C bases to enhance annealing of the end which will be extended. The overall direction of the lagging strand will be 3 to 5, and that of the leading strand 5 to 3. One common method is based on restriction enzymes and DNA ligase. During DNA replication (copying), most DNA polymerases can "check their work" with each base that they add. The new strand will be complementary to the parental or old strand. Separating the strands of the double helix would provide two templates for the synthesis of new complementary strands, but exactly how new DNA molecules were constructed was still unclear. The theoretical amplification value is never achieved in practice. How long does the process of cutting DNA take? True True or false: DNA technology is useful in identification because no two humans, except for identical twins, have the same type of tandem repeats in a strand of DNA. When the leading strand is being synthesized, what direction is the template strand? The replication forks are formed as the double strands of DNA are separated by helicase in both directions away from the origin of replication. Purines have two rings in their base structures,while pyrimidines have a single ring in their base structures. The enzyme ribonuclease H (RNase H), instead of a DNA polymerase as in bacteria, removes the RNA primer, which is then replaced with DNA nucleotides. At least 18 different proteins work together to remove this deformity, using the non-damaged strand as a template to repair the damaged strand. The essential steps of replication in eukaryotes are the same as in prokaryotes. Cloning involves the replication of one molecule to produce a population of cells with identical DNA molecules. In this way, the ends of the chromosomes are replicated. During replication, one strand, which is complementary to the 3 to 5 parental DNA strand, is synthesized continuously toward the replication fork because polymerase can add nucleotides in this direction. Creative Commons Attribution-NonCommercial 4.0 International License, Differentiate between mismatch repair and nucelotide excision repair, Explain the role of ultraviolet light in causing DNA mutations. Dystrophin is one of the longest genes, with 2.4 million base pairs. Although the other answer is funnier, what would actually happen if the gap never closed during a ligation is that the DNA fragments would come apart again. Key points: Polymerase chain reaction, or PCR, is a technique to make many copies of a specific DNA region in vitro (in a test tube rather than an organism). What is PCR used for? Some cells were allowed to grow for one more generation in 14N and spun again. This model for replication suggests that the two strands of the double helix separate during replication, and each strand serves as a template from which the new complementary strand is copied (Figure 2). As a semiconservative process, a single molecule containing two strands of DNA in double helix formation is separated, where each strand serves as a template for the new DNA molecules. Being a highly regulated process, multiple proteins are required both during and following replication to quickly correct mistakes and damages. What direction does DNA polymerase synthesize new DNA strands? What if there are not restriction enzymes on either side of the target DNA? This is known assemiconservative replication. Because DNA is critical to life, research continues to better understand and treat diseases caused by mutations and damages in an individuals DNA. The elucidation of the structure of the double helix provided a hint as to how DNA is copied. Telomerase uses an internal RNA template to provide the complimentary base pairings in telomere synthesis. In fact, billions of molecules of DNA are used in a single ligation! https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-cloning-tutorial/a/bacterial-transformation-selection, https://www.khanacademy.org/science/biology/biotech-dna-technology#dna-sequencing-pcr-electrophoresis, https://en.wikipedia.org/wiki/DNA_profiling. DNA Replication. The helix structure is unwound. Because this sequence allows the start of DNA synthesis, it is appropriately called the primer. Direct link to tyersome's post A typical plasmid can acc. [1] DNA replication occurs in all living organisms acting as the most essential part of biological inheritance. These molecules are all bumping into one another, and into DNA ligase, at random in different ways. Using ATP as an energy source, ligase catalyzes a reaction in which the phosphate group sticking off the 5 end of one DNA strand is linked to the hydroxyl group sticking off the 3 end of the other. This process. Biologydictionary.net Editors. DNA replication is a highly regulated molecular process where a single molecule of DNA is duplicated to result in two identical DNA molecules. Recall that AT sequences have fewer hydrogen bonds and, hence, have weaker interactions than guanine-cytosine (GC) sequences. For bacterial DNA replication to begin, the supercoiled chromosome is relaxed by topoisomerase II, also called DNA gyrase. Is it destroyed? This process takes us from one starting molecule to two "daughter" molecules, with each newly formed double helix containing one new and one old strand. As in prokaryotes, the eukaryotic DNA polymerase can add nucleotides only in the 5 to 3 direction. If two DNA molecules have matching ends, they can be joined by the enzyme. True or False: DNA replication is accomplished using a technique known as polymerase chain reaction. This is accomplished through the activity of bacterial topoisomerase IV, which introduces double-stranded breaks into DNA molecules, allowing them to separate from each other; the enzyme then reseals the circular chromosomes. Srinivas, N., Rachakonda, S., & Kumar, R. (2020). Check out this, Posted 7 years ago. Direct link to Asha Karmakar's post We are not exactly "pasti, Posted 4 years ago. However, for UV radiation specifically, prokaryotes use an enzyme known as photolyase to detect this damage and make repairs. During the replication process, an entirely new strand of DNA is created by using the original template strand and matching the complimentary bases. Specifically,the phosphate is found on the 5 carbon of one nucleotide, while ahydroxyl group (-OH) is found on the 3 carbon of the next nucleotides sugar group. Recall that adenine nucleotides pair with thymine nucleotides . In Repli-seq (A-B), cells are incubated with BrdU, 2-6 fractions of S phase cells are sorted (five fractions are shown in B), and BrdU-containing DNA is sequenced. ). Boston: Pearson Learning. When nucleotides are built in processes such as DNA replication and gene expression, these directions are incredibly important since nucleic acids can only form new bonds on the 3' end. it serves to stabilize the duplex interaction. For more information on the wide range of viral replication strategies, see The Viral Life Cycle. The origin of replication is approximately 245 base pairs long and is rich in adenine-thymine (AT) sequences. The nicks that remain between the newly synthesized DNA (that replaced the RNA primer) and the previously synthesized DNA are sealed by the enzyme DNA ligase that catalyzes the formation of covalent phosphodiester linkage between the 3-OH end of one DNA fragment and the 5 phosphate end of the other fragment, stabilizing the sugar-phosphate backbone of the DNA molecule. Direct link to loganbro45's post what would happen if the , Posted 7 years ago. The Tm of primer hybridization can be calculated using various formulas. Suppose we have a target gene, flanked with, We start off with a target gene and a circular plasmid. Additionally, prokaryotes only have a single origin of replication, while eukaryotes have multiple origins of replication. When two DNA copies are formed, they have an identical sequence of nucleotide bases and are divided equally into two daughter cells. Direct link to 's post It depends on the enzyme , Posted 7 years ago. DNA polymerase III binds to the primer and creates a short segment of newly synthesized DNA from 5-3. Therefore, if the first strand starts at the 3 end and finishes at the 5 end, then the second strand must run opposite, starting at the 5 end and finishing at the 3 end. A typical plasmid can accommodate inserts of any size up to total size of around 50 kb, but plasmids that are more than 20 kb are very difficult to work with and may require special transformation techniques. At the origin of replication, a prereplication complex composed of several proteins, including helicase, forms and recruits other enzymes involved in the initiation of replication, including topoisomerase to relax supercoiling, single-stranded binding protein, RNA primase, and DNA polymerase. These ends thus remain unpaired and, over time, they may get progressively shorter as cells continue to divide. Typically, substantial reduction in yield is observed when the primers extend from each other beyond ~3 Kb. When the replication fork reaches the end of the linear chromosome, there is no place to make a primer for the DNA fragment to be copied at the end of the chromosome. Because eukaryotic DNA is linear, they have ends that create a challenge. Some are blunt cutters, which cut straight down the middle of a target sequence and leave no overhang. So, if multiple products can be made, all of them, How can we avoid the "bad" plasmids? Restriction enzymes are found in bacteria (and other prokaryotes). Direct link to suncoats1's post I did not understand how , Posted 7 years ago. e. Chromosomal DNA is typically wrapped around histones (in eukaryotes and archaea) or histone-like proteins (in bacteria), and is supercoiled, or extensively wrapped and twisted on itself. Mismatch repair enzymes recognize the wrongly incorporated base and excise it from the DNA, replacing it with the correct base (Figure 3b). The elucidation of the structure of the double helix by James Watson and Francis Crick in 1953 provided a hint as to how DNA is copied during the process of replication. 2. This reaction produces an intact sugar-phosphate backbone. What happens to the restriction enzyme once the recombinant plasmid has been formed. Biological science (Sixth edition. Beyond its role in initiation, topoisomerase also prevents the overwinding of the DNA double helix ahead of the replication fork as the DNA is opening up; it does so by causing temporary nicks in the DNA helix and then resealing it. The replication of nuclear and mitochondrial DNA are basic processes assuring the doubling of the genetic information of eukaryotic cells. These enzymes require ATP hydrolysis. poly dG) or repeating motifs - these can hybridize with inappropriate register on the template. DNA replication of the leading strand when the 3-5 template strand is used is as follows: DNA polymerase can only create new DNA strands from 5-3. How does telomerase recognize what bases to add to the lagging strand and where to start? For more information on the wide range of viral replication strategies, see The Viral Life Cycle. For example, UV radiation found in sunlight and tanning booths can create a thymine dimer where two thymine bases next to each other form a covalent bond. When we, Do you want to learn more about restriction enzymes? The most commonly used formula is: Major product should be a duplex DNA molecule whose 5' and 3' ends are defined by the two PCR primers, Other products can, however, be produced. DNA replication is a process that occurs during cellular division where two identical molecules of DNA are created from a single molecule of DNA. Molecular cloning is used to assemble recombinant DNA molecules and to direct their replication within host organisms, making multiple DNA molecules. In the conservative model, parental DNA strands (blue) remained associated in one DNA molecule while new daughter strands (red) remained associated in newly formed DNA molecules. This means that approximately 1000 nucleotides are added per second. DNA must be fully replicated before cells divide via mitosis to ensure all daughter cells have identical DNA. Rolling circle replication begins with the enzymatic nicking of one strand of the double-stranded circular molecule at the double-stranded origin (dso) site. Adenine and guanine are classified as purines, while cytosine and thymine are classified as pyrimidines. The leading strand can be extended from one primer alone, whereas the lagging strand needs a new primer for each of the short Okazaki fragments. As the DNA opens up, Y-shaped structures called replication forks are formed. The nitrogenous bases stick out from this backbone. A second DNA strand ismatched to this first strand based on complimentary base pairing, where a single purine pairs with a single pyrimidine. The interpretation of this formula is that. Once single-stranded DNA is accessible at the origin of replication, DNA replication can begin. If they are not, mutations can result. Direct link to Hafsa Abdinur's post I am quite confused as to, Posted 7 years ago. Miesfeld, R. & McEvoy, M. (2017). Nucleotides are arranged into chains that become individual strands of DNA, which is half of a full DNA molecule. Restriction digests and ligations like this one are performed using many copies of plasmid and gene DNA. This thus creates a bump in the DNA strand that prevents DNA polymerase from synthesizing past this point. However, DNA pol III is able to add nucleotides only in the 5 to 3 direction (a new DNA strand can be only extended in this direction). Primers are placed on the telomere where DNA polymerase III can attach to synthesize the final portion of DNA leftover on the lagging strand. The two segments are now connected into a single strand. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. To solve this issue, telomeres are present in eukaryotes. It attaches to the end of the chromosome, and complementary bases to the RNA template are added on the 3 end of the DNA strand. The sliding clamp stabilizes DNA polymerase III. These results could only be explained if DNA replicates in a semiconservative manner. Theme 4: How Do Diet, Exercise and Weight Affect Health? 2. To be used as a template, the double helix must first be opened up and the two strands separated to expose unpaired bases. The leading strand is continuously synthesized by the eukaryotic polymerase enzyme pol , while the lagging strand is synthesized by pol .
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dna replication is accomplished using a technique known as: 2023