James Watson and Francis Crick
In 1953 scientists, James Watson and Francis Crick , were trying to put together a model of DNA. When they saw Franklin and Wilkin's picture of the X-ray they had information to make an correct model.
They created a model that has not been changed much since then. Their model showed a double helix with tiny rungs connecting the strands. These rungs were the bases of a nucleotide (see nucleic acids). At first Watson and Crick were set back with a controversy, how to bond the bases together, and how to solve the issue of the sizes of the bases. Adenine and Guanine were purines having carbon-nitrogen rings in their structures.
Thymine and Cytosine were pyrimidines having carbon-nitrogen ring in its structure. If DNA were to have its bases pair up so that the purines and the pyrimidines were together, then it would look wobly and crooked. Watson and Crick then found that in the event that they paired Thymine with Adenine and Guanine with Cytosine DNA would look uniform. This pairing was also in accordance with Cargaff's rule. They also found that a hydrogen bond could be formed between the pairs of bases. In all DNA strands if side has a Thymine base then the other has the opposite: Adenine and so on with Guanine and Cytosine. Each side is a complete compliment of the other.
In 1953 scientists, James Watson and Francis Crick , were trying to put together a model of DNA. When they saw Franklin and Wilkin's picture of the X-ray they had information to make an correct model.
They created a model that has not been changed much since then. Their model showed a double helix with tiny rungs connecting the strands. These rungs were the bases of a nucleotide (see nucleic acids). At first Watson and Crick were set back with a controversy, how to bond the bases together, and how to solve the issue of the sizes of the bases. Adenine and Guanine were purines having carbon-nitrogen rings in their structures.
Thymine and Cytosine were pyrimidines having carbon-nitrogen ring in its structure. If DNA were to have its bases pair up so that the purines and the pyrimidines were together, then it would look wobly and crooked. Watson and Crick then found that in the event that they paired Thymine with Adenine and Guanine with Cytosine DNA would look uniform. This pairing was also in accordance with Cargaff's rule. They also found that a hydrogen bond could be formed between the pairs of bases. In all DNA strands if side has a Thymine base then the other has the opposite: Adenine and so on with Guanine and Cytosine. Each side is a complete compliment of the other.
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