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1952: an X-ray diffraction image of DNA was taken by Raymond Gosling in May 1952, a student supervised by Rosalind Franklin. [30] 1953: DNA structure is resolved to be a double helix by James Watson, Francis Crick and Maurice Wilkins. [31] 1955: Alexander R. Todd determined the chemical makeup of nitrogenous bases.
Using these x-rays and information already known about the chemistry of DNA, James D. Watson and Francis Crick demonstrated the molecular structure of DNA in 1953. [ 22 ] [ 23 ] Together, these discoveries established the central dogma of molecular biology , which states that proteins are translated from RNA which is transcribed by DNA.
Rosalind Franklin joined King's College London in January 1951 to work on the crystallography of DNA. By the end of that year, she established two important facts: one is that phosphate groups, which are the molecular backbone for the nucleotide chains, lie on the outside (it was a general consensus at the time that they were at the inside); and the other is that DNA exists in two forms, a ...
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 ...
All known DNA replication systems require a free 3′ hydroxyl group before synthesis can be initiated (note: the DNA template is read in 3′ to 5′ direction whereas a new strand is synthesized in the 5′ to 3′ direction—this is often confused). Four distinct mechanisms for DNA synthesis are recognized: [citation needed]
DNA can be copied very easily and accurately because each piece of DNA can direct the assembly of a new copy of its information. This is because DNA is made of two strands that pair together like the two sides of a zipper. The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together.
In its modern sense, molecular biology attempts to explain the phenomena of life starting from the macromolecular properties that generate them. Two categories of macromolecules in particular are the focus of the molecular biologist: 1) nucleic acids , among which the most famous is deoxyribonucleic acid (or DNA), the constituent of genes , and ...
DNA replication also works by using a DNA template, the DNA double helix unwinds during replication, exposing unpaired bases for new nucleotides to hydrogen bond to. Gene synthesis, however, does not require a DNA template and genes are assembled de novo. DNA synthesis occurs in all eukaryotes and prokaryotes, as well as some viruses. The ...