DNA Structure





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Uploaded on Dec 15, 2010

The DNA structure consists of two chainlike molecules (polynucleotides) that twist around each other to form the classic double-helix. The cell's machinery forms polynucleotide chains by linking together four nucleotides. The nucleotides which are used to build DNA chains are adenosine (A), guanosine (G), cytidine (C), and thymidine (T). The DNA structure houses the information required to make all the polypeptides used by the cell. The sequence of nucleotides in DNA strands (called a 'gene') specifies the sequence of amino acids in polypeptide chains.

Clearly a one-to-one relationship cannot exist between the four nucleotides of DNA and the twenty amino acids used to assemble polypeptides. The cell therefore uses groupings of three nucleotides (called 'codons') to specify twenty different amino acids. Each codon specifies an amino acid.

Because some codons are redundant, the amino acid sequence for a given polypeptide chain can be specified by several different nucleotide sequences. In fact, research has confirmed that the cell does not randomly make use of redundant codons to specify a particular amino acid in a polypeptide chain. Rather, there appears to be a delicate rationale behind codon usage in genes.

DNA structure -- Information and Design
The molecular constituents of the DNA structure appear to have optimized chemical properties to produce a stable helical structure capable of storing the information required for the cell's operation. Detailed accounts of how such an optimized structure for the cell's most fundamental information storage medium could have arisen naturally have not been produced. To suppose that such extensive optimization could have come into being by blind chance is a far greater leap of faith than many would be willing to take.

For more specifics on the DNA structure, please visit http://www.allaboutscience.org/dna-st...

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