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The replication fork is a structure that forms within the long helical DNA during DNA replication. It is produced by enzymes called helicases that break the hydrogen bonds that hold the DNA strands together in a helix. The resulting structure has two branching "prongs", each one made up of a single strand of DNA.
DNA is a macromolecule made up of nucleotide units, which are linked by covalent bonds and hydrogen bonds, in a repeating structure. DNA synthesis occurs when these nucleotide units are joined to form DNA; this can occur artificially (in vitro) or naturally (in vivo). Nucleotide units are made up of a nitrogenous base (cytosine, guanine ...
The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, the single-ringed pyrimidines and the double-ringed purines. In DNA, the pyrimidines are ...
The involved saccharide groups are deoxyribose in DNA and ribose in RNA. In order for the phosphodiester bond to form, joining the nucleosides, the tri-phosphate or di-phosphate forms of the nucleotide building blocks are broken apart to give off energy required to drive the enzyme-catalyzed reaction. [4]
The double-helix model of DNA structure was first published in the journal Nature by James Watson and Francis Crick in 1953, [6] (X,Y,Z coordinates in 1954 [7]) based on the work of Rosalind Franklin and her student Raymond Gosling, who took the crucial X-ray diffraction image of DNA labeled as "Photo 51", [8] [9] and Maurice Wilkins, Alexander Stokes, and Herbert Wilson, [10] and base-pairing ...
Loads Mcm2-7 complex on DNA at ORC in pre-RC/licensing step. Inhibited in metazoans by geminin. Claspin: Couple leading-strand synthesis with the CMG complex helicase activity. Works with Mrc1 Ctf4: Loads DNA polymerase α onto chromatin together with CMG complex on the lagging strand. Homolog in metazoans is known as AND-1. Cyclin-dependent ...
This gives the RNA and DNA their unmistakable 'ladder-step' order of nucleotides within their molecules. Both play a crucial role in directing protein synthesis. Strings of nucleotides are bonded to form spiraling backbones and assembled into chains of bases or base-pairs selected from the five primary, or canonical, nucleobases. RNA usually ...
When deoxyribonucleotides polymerize to form DNA, the phosphate group from one nucleotide will bond to the 3' carbon on another nucleotide, forming a phosphodiester bond via dehydration synthesis. New nucleotides are always added to the 3' carbon of the last nucleotide, so synthesis always proceeds from 5' to 3'.