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For semiconservative replication to occur, the DNA double-helix needs to be separated so the new template strand can be bound to the complementary base pairs. Topoisomerase is the enzyme that aids in the unzipping and recombination of the double-helix. Specifically, topoisomerase prevents the double-helix from supercoiling, or becoming too ...
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 ...
Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3′ hydroxyl group (—OH) on the other. 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 ]
Frumkin perfected a test that can differentiate real DNA samples from fake ones. His test detects epigenetic modifications, in particular, DNA methylation. [91] Seventy percent of the DNA in any human genome is methylated, meaning it contains methyl group modifications within a CpG dinucleotide context. Methylation at the promoter region is ...
By convention, if the base sequence of a single strand of DNA is given, the left end of the sequence is the 5′ end, while the right end of the sequence is the 3′ end. The strands of the double helix are anti-parallel, with one being 5′ to 3′, and the opposite strand 3′ to 5′.
They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA and RNA. Dictated by specific hydrogen bonding patterns, "Watson–Crick" (or "Watson–Crick–Franklin") base pairs ( guanine – cytosine and adenine – thymine ) [ 1 ] allow the DNA helix to maintain a regular helical structure that is ...
The vast majority of DNA damage affects the primary structure of the double helix; that is, the bases themselves are chemically modified. These modifications can in turn disrupt the molecules' regular helical structure by introducing non-native chemical bonds or bulky adducts that do not fit in the standard double helix.
A-DNA is one of the possible double helical structures which DNA can adopt. A-DNA is thought to be one of three biologically active double helical structures along with B-DNA and Z-DNA . It is a right-handed double helix fairly similar to the more common B-DNA form, but with a shorter, more compact helical structure whose base pairs are not ...