Discontinuous replication

The top strand must be discontinuously replicated in short stretches thus tlie replication of both parental strands is a semidiscontinuous process. The strand that is continuously sy thesized is called the leading strand while the strand that is discontinuously synthesized is called the lagging strand. 

DNA strands, synthesis of one new strand of DNA can be continuous but synthesis along the other strand must occur by discontinuous replication. 

Okazaki fragments Short DNA segments generated during discontinuous replication of the lagging strand these were described by Reiji Okazaki, based on experiments using radioactive deoxynucleotides as precursors in DNA synthesis. 

Define continuous replication and discontinuous replication and relate these terms to the leading and lagging strands of replicating DNA. Describe an Okazaki fragment. 

FIGURE 11.36 Discontinuous replication of DNA with Okazaki fragments. 

Foam generated in porous media consists of a gas (or a liquid) dispersed in a second interconnected wetting liquid phase, usually an aqueous surfactant solution (1). Figure 1 shows a micrograph of foam flowing in a two-dimensional etched-glass porous medium micromodel (replicated from a Kuparuk sandstone, Prudhoe Bay, Alaska (2)). Observe that the dispersion microstructure is not that of bulk foam. Rather discontinuous... 

At each replication fork there are two DNA polymerase complexes. As the double-stranded DNA is unwound, two template strands are exposed. One of the templates can be replicated in a continuous fashion by DNA polymerase since a continuous synthesis of new strands can occur in the 5 to 3 direction as the template strand is exposed. Since all growing chains must be synthesized in file 5 to 3 direction, the lagging chain must be continuously reinitiated as new template is exposed. The lagging strand is then synthesized discontinuously, in pieces that must be joined together later. 

Figure 17. Mean skew profile of intergenic regions around putative replication origins [38]. The skew S was calculated in 1 kbp windows (Watson strand) around the position ( 300 kbp without repeats) of the 1012 detected upward jumps 5 and 3 transcript extremities were extended by 0.5 and 2 kbp, respectively ( ), or by 10 kbp at both ends ( ). The abscissa represents the distance (in kbp) to the corresponding origin the ordinate represents the skews calculated for the windows situated in intergenic regions (mean values for all discontinuities and for 10 consecutive 1-kbp window positions). The skews are given in percent (vertical bars, SEM). The lines correspond to linear fits of the values of the skew ( ) for n < —100 kbp and n > 100 kbp.

Replication on the l ging strand is discontinuous because polymerases can... 

Baldessarini, R.J., Tondo, L., Floris, G., and Rudas, N. (1997) Reduced morbidity aftet gtadual discontinuation of lithium treatment for bipolar I and II disorders a replication study. Am J Psychiatry 154 551—553. 

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. 

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. 

Growth during Replication Is Bidirectional Growth at the Replication Forks Is Discontinuous Proteins Involved in DNA Replication Characterization of DNA Polymerase I in Vitro Crystallography Combined with Genetics to Produce a Detailed Picture of DNA Poll Function... 

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