Replication/synthesis

Phenol was reported to induce DNA oxidative damage in human promyelocytic HL60 cells and to inhibit repair of radiation-induced chromosomal breaks in human leukocytes (Morimoto et al., 1976). However, it only slightly inhibited DNA repair synthesis and DNA replication synthesis in WI-38 human diploid fibroblasts (Poirier et al., 1975). 

Figure 37.2 A simplified schematic view of cell cycle progression in diatoms, with critical arrest points and dominant processes indicated. Most diatoms arrest at the Gl/S boundary, but a secondary arrest point can occur during the G2/M phase. M mitosis S DNA replication (synthesis) G1 and G2 gap phases.

Nucleus The nucleus is the "Control Center" of the cell, which contains DNA (genetic information) in the form of genes, and also information for the formation of proteins. Information is carried on chromosomes, which are a form of DNA. Site for DNA replication, synthesis and processing of messenger RNA s. 

When a molecule of DNA is replicated, each of the two strands is used as a template to create a complementary strand. When a cell divides into two, each of the two cells has one of the original template strands and one of the new strands. This process is called semiconservative replication. When DNA molecules are rephcated, the strands are separated at origins of replications. Synthesis occurs in both directions from the origin along replication forks. 

Telomere replication, (a) In replication of the lagging strand, short RNA primers are added (pink) and extended hy DNA polymerase. When the RNA primer at the 5 end of each strand is removed, there is no nucleotide sequence to read in the next round of DNA replication. The result is a gap (primer gap) at the 5 end of each strand (only one end of a chromosome is shown in this figure), (h) Asterisks indicate sequences at the 3 end that cannot he copied hy conventional DNA replication. Synthesis of telomeric DNA hy telomerase extends the 5 ends of DNA strands, allowing the strands to he copied hy normal DNA replication. 

Prebiotic peptides, peptides formed before the origin of life. Most likely, amino acids were already present on primitive Earth. They are supposed to have been produced in the primitive atmosphere, in hydrothermal vents, or to have been imported in meterorites. a-Amino acids can undergo peptide formation by activation with carbon monoxide under hot aqueous conditions in the presence of freshly co-precipitated colloidal (Fe,Ni)S. Peptides may have been formed via —>-N-carboxy anhydrides. A replicative synthesis involving aminoacyl-RNA intermediates has also been suggested. The question of whether a peptide/protein world preceded the RNA-driven template synthesis, or whether RNA and proteins should not be viewed as eti-ologically discrete entities in the origin of life, is still under debate [V. Borsenberger et al., Chem. Biodivers. 2004, 1, 203 C. Huber et al., Science 2003, 301, 938 A. Brack, Chem. Biodivers. 2007, 4, 665]. 

A decrease in the activity of primase would account for the low rate of DNA replication. Synthesis of DNA itself requires the prior synthesis of RNA primers. Also, decreased rates of dNTP synthesis could slow replication. 

Millner GC, Shaddock JG, Harbison RD, et al. 1988. A comparison between the in vitro DNA repair assay and the in vivo/in vitro DNA repair and DNA replicative synthesis assays for detecting hepatocarcinogens [Abstract]. Environ Mol Mutagen 11 70. 

Structure replication Synthesis of high surface area materials For many metal oxides two-step process (template of silica matrix + nanocasting) required... 

Fig. 2.10 The polymerase chain reaction (PCR). Vertical arrows indicate the heat-induced dissociation of the double strands and the association with the primers. Horizontal arrows symbolize the DNA replication (synthesis) step. With each cycle, the number of DNA strands containing the sequence of interest is doubled. See Box 3 for more details.

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