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Francis Harry Compton Crick OM FRS [3] [4] (8 June 1916 – 28 July 2004) was an English molecular biologist, biophysicist, and neuroscientist.He, James Watson, Rosalind Franklin, and Maurice Wilkins played crucial roles in deciphering the helical structure of the DNA molecule.
The two base-pair complementary chains of the DNA molecule allow replication of the genetic instructions. The "specific pairing" is a key feature of the Watson and Crick model of DNA, the pairing of nucleotide subunits. [5] In DNA, the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. The A:T and C:G pairs ...
Starting in the mid-1950s, Arthur Kornberg began to study the mechanism of DNA replication. [4] By 1957 he has identified the first DNA polymerase. [5] The enzyme was limited, creating DNA in just one direction and requiring an existing primer to initiate copying of the template strand.
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.
The results showed that after one generation of replication in the 14 N medium, the DNA formed a band of intermediate density between that of pure 15 N DNA and pure 14 N DNA. This supported the semiconservative DNA replication proposed by Watson and Crick, where each strand of the parental DNA molecule serves as a template for the synthesis of ...
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.
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.
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 ...