where does the synthesis of new dna from existing dna occurs
origins of replication
title: DNA synthesis text: DNA synthesis DNA synthesis is the natural or artificial creation of deoxyribonucleic acid (DNA) molecules. The term DNA synthesis can refer to DNA replication - DNA biosynthesis ("in vivo" DNA amplification), polymerase chain reaction - enzymatic DNA synthesis ("in vitro" DNA amplification) or gene synthesis - physically creating artificial gene sequences. In nature, DNA molecules are created by all living cells through the process of DNA replication, with replication initiator proteins splitting the cell's DNA and copying each split strand, with the copied strands then joining together with their template strand into a new DNA molecule. Various means exist to title: DNA replication text: the new helix will be composed of an original DNA strand as well as a newly synthesized strand. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication. In a cell, DNA replication begins at specific locations, or origins of replication, in the genome. Unwinding of DNA at the origin and synthesis of new strands, accommodated by an enzyme known as helicase, results in replication forks growing bi-directionally from the origin. A number of proteins are associated with the replication fork to help in the initiation and continuation of DNA synthesis. Most prominently, DNA polymerase synthesizes the new title: DNA synthesis text: biology. New nucleobase pairs can also be synthesized, A-T (adenine - thymine) and G-C (guanine - cytosine). A third base pair would expand the number of amino acids that can be encoded by DNA from the existing 20 amino acids to a possible 172. DNA synthesis DNA synthesis is the natural or artificial creation of deoxyribonucleic acid (DNA) molecules. The term DNA synthesis can refer to DNA replication - DNA biosynthesis ("in vivo" DNA amplification), polymerase chain reaction - enzymatic DNA synthesis ("in vitro" DNA amplification) or gene synthesis - physically creating artificial gene sequences. In nature, DNA molecules are title: DNA replication text: synthesis of new strands, but can only extend an existing DNA or RNA strand paired with a template strand. To begin synthesis, a short fragment of RNA, called a primer, must be created and paired with the template DNA strand. DNA polymerase adds a new strand of DNA by extending the 3' end of an existing nucleotide chain, adding new nucleotides matched to the template strand one at a time via the creation of phosphodiester bonds. The energy for this process of DNA polymerization comes from hydrolysis of the high-energy phosphate (phosphoanhydride) bonds between the three phosphates attached to each title: Homologous recombination text: between the invading 3' overhang strand and the homologous chromosome. After strand invasion, a DNA polymerase extends the end of the invading 3' strand by synthesizing new DNA. This changes the D-loop to a cross-shaped structure known as a Holliday junction. Following this, more DNA synthesis occurs on the invading strand (i.e., one of the original 3' overhangs), effectively restoring the strand on the homologous chromosome that was displaced during strand invasion. After the stages of resection, strand invasion and DNA synthesis, the DSBR and SDSA pathways become distinct. The DSBR pathway is unique in that the second 3' overhang