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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 ...
Bind to ssDNA and prevent the DNA double helix from re-annealing after DNA helicase unwinds it, thus maintaining the strand separation, and facilitating the synthesis of the new strand. Topoisomerase: Relaxes the DNA from its super-coiled nature. DNA gyrase: Relieves strain of unwinding by DNA helicase; this is a specific type of topoisomerase ...
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 process of semiconservative replication for the site of DNA replication is a fork-like DNA structure, the replication fork, where the DNA helix is open, or unwound, exposing unpaired DNA nucleotides for recognition and base pairing for the incorporation of free nucleotides into double-stranded DNA.
Double-strand breaks, in which both strands in the double helix are severed, are particularly hazardous to the cell because they can lead to genome rearrangements. In fact, when a double-strand break is accompanied by a cross-linkage joining the two strands at the same point, neither strand can be used as a template for the repair mechanisms ...
The dispersive hypothesis is exemplified by a model proposed by Max Delbrück, which attempts to solve the problem of unwinding the two strands of the double helix by a mechanism that breaks the DNA backbone every 10 nucleotides or so, untwists the molecule, and attaches the old strand to the end of the newly synthesized one. This would ...
Helicases are motor proteins that move directionally along a nucleic double helix, separating the two hybridized nucleic acid strands (hence helic-+ -ase), via the energy gained from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed.
The comet assay (single-cell gel electrophoresis) is a simple method for measuring deoxyribonucleic acid (DNA) strand breaks in eukaryotic cells. Cells embedded in agarose on a microscope slide are lysed with detergent and high salt to form nucleoids containing supercoiled loops of DNA linked to the nuclear matrix.