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Double-stranded RNA forms an A-type helical structure, unlike the common B-type conformation taken by double-stranded DNA molecules. The secondary structure of RNA consists of a single polynucleotide. Base pairing in RNA occurs when RNA folds between complementarity regions. Both single- and double-stranded regions are often found in RNA molecules.
For DNA, with its double helix, there are two possible directions for the notated sequence; of these two, the sense strand is used. Because nucleic acids are normally linear (unbranched) polymers , specifying the sequence is equivalent to defining the covalent structure of the entire molecule.
The double-stranded structure of DNA provides a simple mechanism for DNA replication. Here, the two strands are separated and then each strand's complementary DNA sequence is recreated by an enzyme called DNA polymerase. This enzyme makes the complementary strand by finding the correct base through complementary base pairing and bonding it onto ...
The following table is a representative sample of Erwin Chargaff's 1952 data, listing the base composition of DNA from various organisms and support both of Chargaff's rules. [17] An organism such as φX174 with significant variation from A/T and G/C equal to one, is indicative of single stranded DNA.
Transcription of single-stranded RNA from a double-stranded DNA template requires the selection of one strand of the DNA template as the template strand that directly interacts with the nascent RNA due to complementary sequence. The other strand is not copied directly, but necessarily its sequence will be similar to that of the RNA.
The chemical structure of DNA base-pairs . A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA.
Double-stranded nucleic acids are made up of complementary sequences, in which extensive Watson-Crick base pairing results in a highly repeated and quite uniform nucleic acid double-helical three-dimensional structure. [24] In contrast, single-stranded RNA and DNA molecules are not constrained to a regular double helix, and can adopt highly ...
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 ...