Editing Nucleoside triphosphate (section)

== DNA and RNA synthesis ==
[[File:DNA synthesis EN.png|thumb|385x385px|In nucleic acid synthesis, the 3’ OH of a growing chain of nucleotides attacks the α-phosphate on the next NTP to be incorporated (blue), resulting in a phosphodiester linkage and the release of pyrophosphate (PP<sub>i</sub>). This figure shows DNA synthesis, but RNA synthesis occurs through the same mechanism.]]The cellular processes of [[DNA replication]] and [[Transcription (biology)|transcription]] involve DNA and RNA synthesis, respectively. DNA synthesis uses dNTPs as substrates, while RNA synthesis uses rNTPs as substrates.<ref name=":8" /> NTPs cannot be converted directly to dNTPs. DNA contains four different nitrogenous bases: [[adenine]], [[guanine]], [[cytosine]] and [[thymine]]. RNA also contains adenine, guanine, and cytosine, but replaces thymine with [[uracil]].<ref>{{Cite news|url=https://www.thoughtco.com/dna-versus-rna-608191|title=Do You Know the Differences Between DNA and RNA?|work=ThoughtCo|access-date=2017-11-11}}</ref> Thus, DNA synthesis requires dATP, dGTP, dCTP, and dTTP as substrates, while RNA synthesis requires ATP, GTP, CTP, and UTP.

Nucleic acid synthesis is catalyzed by either [[DNA polymerase]] or [[RNA polymerase]] for DNA and RNA synthesis respectively.<ref>{{Cite web|url=http://www.differencebetween.com/difference-between-dna-polymerase-and-vs-rna-polymerase/|title=Difference Between DNA Polymerase and RNA Polymerase|access-date=2017-11-11|date=2011-12-24}}</ref> These enzymes [[Covalent bond|covalently]] link the free [[Hydroxy group|-OH]] group on the 3’ carbon of a growing chain of nucleotides to the α-phosphate on the 5’ carbon of the next (d)NTP, releasing the β- and γ-phosphate groups as [[pyrophosphate]] (PP<sub>i</sub>).<ref name=":2">{{cite book | vauthors = Lodish H, Berk A, Zipursky SL, Matsudaira P, Baltimore D, Darnell J |date=2000|title=Nucleic Acid Synthesis|url=https://www.ncbi.nlm.nih.gov/books/NBK21644/}}</ref> This results in a [[Phosphodiester bond|phosphodiester]] linkage between the two (d)NTPs. The release of PP<sub>i</sub> provides the energy necessary for the reaction to occur.<ref name=":2" /> Nucleic acid synthesis occurs exclusively in the [[Directionality (molecular biology)|5’ to 3’ direction]].