Replication leading strand

Biological function Lagging strand replication DNA repair Mitochondrial DNA replication Leading strand replication Replicadoi... 

Leading strand (Section 28.10) In DNA replication, the strand that grows toward the replication fork. 

LDA, see Lithium diisopropylamide LDL, heart disease and, 1090-1091 Le Bel, Joseph Achille, 7-8 Leading strand, DNA replication and, 1107... 

Registiy of Mass Spectral Data, 412 Replication (DNA). 1106-1107 direction of, 1107 error rate during. 1107 lagging strand in, 1107 leading strand in, 1107 Okazaki fragments in, 1107 replication fork in, 1107 Replication fork (DNA), 1107 Reserpine, structure of, 65 Residue (protein), 1027 Resist, photolithography and, 505-506... 

Each strand of the double helix is replicated simultaneously but by somewhat different mechanisms. A complex of proteins, including DNA polymerase, replicates the leading strand continuously in the 5 to 3 direction. The lagging strand is replicated discon-tinuously, in short pieces of 150-250 nucleotides, in the 3 to 5 direction. 

DNA replication differs between the leading strand and the lagging strand of the DNA double helix. In cells, replication Af the lagging strand involves the formation of short RNA primers by action of an enzyme called RNA primase (or primase for short). Such RNA primers are made at intervals on the lagging strand and are then removed and replaced with DNA by DNA polymerase. 

Figure 5.14 Events in the replication of < >X174 DNA. (a) Formation of the replicating double-stranded DNA (RF). (b) Rolling circle replication leads to the formation of virus progeny.

Eukaryotes Yes No Nuclear replication Continuous (leading) strand replication... 

DNA polymerase 5 synthesizes the leading strand during replication. 

Elongation The elongation phase of replication includes two distinct but related operations leading strand synthesis and lagging strand synthesis. Several enzymes at the replication fork are important to the synthesis of both strands. Parent DNA is first unwound by DNA helicases, and the resulting topological stress is relieved by topo-isomerases. Each separated strand is then stabilized by... 

DNA is synthesized in the 5 —>3 direction by DNA polymerases. At the replication fork, the leading strand is synthesized continuously in the same direction as replication fork movement the lagging strand is synthesized discontinuously as Okazaki fragments, which are subsequently ligated. 

Terms in bold are defined template 950 semiconservative replication 950 replication fork 951 origin 952 Okazaki fragments 952 leading strand 952 lagging strand 952 nucleases 952 exonuclease 952 endonuclease 952 DNA polymerase I 952 primer 954 primer terminus 954... 

Fidelity of Replication of DNA What factors promote the fidelity of replication during the synthesis of the leading strand of DNA Would you expect the lagging strand to be made with the same fidelity Give reasons for your answers. 

Leading strand The strand that is being copied in the direction of the advancing replication fork is called the leading strand and is synthesized almost continuously. 

DNA polymerases are only able to "read" the parental nucleotide template sequences in the 3 ->5 direction and synthesize the new DNA strands in the 5 ->3 (antiparallel) direction. Therefore, beginning with one parental double helix, the two newly synthesized stretches of nucleotide chains must grow in opposite directions—one in the 5 ->3 direction toward the replication fork (leading strand), and one in the 5 —>3 direction away from the replication fork (lagging strand). The lagging strand is synthesized discontinuously. 

There are at least five classes of eukaryotic DNA polymerases. Pol a is a multisubunit enzyme, one subunit of which performs the primase function. Pol a 5 ->3 polymerase activity adds a short piece of DNA to the RNA primer. Pol 8 completes DNA synthesis on the leading strand and elongates each lagging strand fragment, using 3 ->5 exonuclease activity to proofread the newly synthesized DNA. Pol p and pol e are involved in carrying out DNA "repair," and pol y replicates mitochondrial DNA. 

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