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The secondary structures of biological DNAs and RNAs tend to be different: biological DNA mostly exists as fully base paired double helices, while biological RNA is single stranded and often forms complex and intricate base-pairing interactions due to its increased ability to form hydrogen bonds stemming from the extra hydroxyl group in the ...
The mRNA stem-loop structure forming at the ribosome binding site may control an initiation of translation. [4] [5] Stem-loop structures are also important in prokaryotic rho-independent transcription termination. The hairpin loop forms in an mRNA strand during transcription and causes the RNA polymerase to become dissociated from the DNA ...
DNA structure and bases A-B-Z-DNA Side View. Tertiary structure refers to the locations of the atoms in three-dimensional space, taking into consideration geometrical and steric constraints. It is a higher order than the secondary structure, in which large-scale folding in a linear polymer occurs and the entire chain is folded into a specific 3 ...
The structural hierarchy in RNA is usually described in terms of a stem-loop 2D secondary structure, which further folds to form its 3D tertiary structure, stabilized by what are referred to as long range tertiary contacts. Most often the non-canonical base pairs are involved in those tertiary contacts or extra-stem base pairs.
Ten years after James Watson and Francis Crick published their model of the DNA double helix, [2] Karst Hoogsteen reported [3] a crystal structure of a complex in which analogues of A and T formed a base pair that had a different geometry from that described by Watson and Crick. Similarly, an alternative base-pairing geometry can occur for G ...
Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing ) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds.
DNA is a long polymer made from repeating units called nucleotides. [6] [7] The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. [8] In all species it is composed of two helical chains, bound to each other by hydrogen bonds.
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 ...