Molecular Biotechnology: Principles and Applications - Glick, B., & Pasternak, J. 2002

Fundamentals of Molecular Biotechnology
DNA, RNA, and Protein Synthesis
Replication

According to the Watson-Crick model, each DNA strand serves as a template for the synthesis of a new complementary strand, with The base sequence in the synthesized (growing) strand being determined by The sequence of complementary bases in the template strand. Each monomer unit added to the growing chain is in the form of a deoxynucleoside 5'-triphosphate (Fig. 3.5); the phosphate group attached to the 5'-carbon atom of deoxyribose is designated as α, followed by the β-phosphate and further by the γ-phosphate. During Replication, the β- and γ-phosphate groups are cleaved off as pyrophosphate, while the α-phosphate group binds to the 3'-OH group of the terminal nucleotide of the growing chain (Fig. 3.6). DNA Synthesis in both PROKARYOTES AND EUKARYOTES involves a multitude of various Enzymes. The primary role is played by DNA polymerase, which sequentially adds new units to the growing polynucleotide chain in accordance with the complementarity principle and catalyzes The formation of phosphodiester bonds.

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Fig. 3.5. Structural formula of deoxynucleoside triphosphate. The phosphate groups are designated by the letters α, β, and γ. The α-phosphate is linked to the 5'-carbon atom of deoxyribose and participates in the Formation of the phosphodiester bond during replication; the β- and γ-phosphate groups are cleaved off as pyrophosphate.

Fig. 3.6. METABOLISM/36.html">DNA replication. A. Pairing of the incoming deoxynucleoside triphosphate with the complementary Base of the DNA template.

In Bacteria, DNA replication begins at a specific locus on the molecule known as THE ORIGIN OF replication (ori). Eukaryotic DNA contains multiple such sites, and replication can initiate at each of them. The resulting segments of eukaryotic DNA are subsequently joined together by specialized enzymes. Furthermore, eukaryotes possess a special enzyme, telomerase, which extends and maintains the ends (telomeres) of Chromosomes.