Leading strands

Because nucleotides are added m the 5 — 3 direction the processes by which the two new chains grow are different Cham growth can be continuous m the leading strand but not m the lagging strand... 

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... 

The multiprotein unit that synthesize RNA by copying the sequence information from the leading strand of the DNA. Its activity is tightly controlled by phosphorylation of the C-termal domain (CTD), access to DNA and interaction by general and sequence specific transcription factors and coactivators and corepressors. 

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. 

Ishmael, F.T., Trakselis, M.A., and Benkovic, S.J. (2003) Protein-protein interactions in the bacteriophage T4 replisome. The leading strand holoenzyme is physically linked to the lagging strand holoenzyme and the primosome./. Biol. Chem. 278, 3145-3152. 

Leading strand = continuous synthesis. Lagging strand = discontinuous synthesis. Order of action ... 

After synthesis, the RNA primers must be removed, gaps filled in, and the strands joined to give a linear, duplex DNA. New histones are added to the lagging strand (which is now a duplex) while the old histones remain with the leading strand. As the smoke slowly clears, we have a copy of the original DNA. 

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

DNA polymerase III begiiis synthesizing DNA in the 5 ->3 direction, beginning at the 3 end of each RNA primer. The newly synthesized strand is complementary and antiparaUd to the parental strand used as a template. This strand can be made continuously in one long piece and is known as the leading strand. ... 

DNA polymerase 5 synthesizes the leading strand during replication. 

Synthesis of DNA Leading strand Lading strand (Okazaki fragments) DNA polymerase III DNA polymerase lU DNA polymerase 6 DNA polymerase a... 

DNA polymerase III (DNA pol HI), the main DNA polymerase of Escherichia coli, synthesizes DNA continuously on the leading strand and discon-tinuously on the lagging strand. 

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... 

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