Re-designed DNA Doesn’t Fit

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Re-designed DNA doesn’t fit, as noted in a brief item in Nature, vol. 440, p604, 10 August 2006. The "D" in DNA stands for deoxyribose, a sugar molecule made from a five sided ring of carbon atoms. Five sided sugars are called pentoses. Most other sugar molecules, such as glucose, are made from six sided rings, and are called hexoses. Chemists have speculated as to why DNA is made from a five sided ring and suggested that the six sided ring would not enable the molecule to form a compact double helix structure.

The journal Nature provides a summary of a study described in J. Am. Chem. Soc. doi:10.1021/ja062548x (2006) as follows: "Few would dispute the genius of DNA's chemical design. But some do question why its backbone evolved to be made from chains of five- rather than six-membered rings, when the latter might more easily be derived from common sugars, such as glucose. Since the idea was first raised in the early 1990s, chemists have suspected that sugars' hexose rings might simply be too bulky to fit into DNA's neat structure. At last, Martin Egli of Vanderbilt University in Nashville, Tennessee, and his colleagues have confirmed this experimentally. They studied the crystal structure of double-stranded homo-DNA, which has hexose in the backbone in place of DNA's deoxyribose. The result was a "slowly writhing ribbon", the team reports, with irregular twists and steps between base pairs."

Editorial Comment: This experiment reminds us that complex molecules like DNA can only be made once the biochemical machinery to make the component parts already exists. To make DNA, cells have to be able to make five-ringed sugars. This is further evidence that DNA and RNA (also made with five ringed sugars) did not evolve by chance before there were any cells to make them. It took clever creative chemists to make the "6 ring" hexose version of DNA, which wouldn’t be suitable for making a compact genetic information storage system. It took a much cleverer, creative chemist to design the molecule that does work – and He didn’t have to experiment first. Those who appreciate the "genius of DNA’s chemical design" have no excuse for refusing to recognise the Genius who designed it and give Him the honour he deserves. (Ref. biochemistry, nucleotides, abiogenesis)

Evidence News 11 October 2006

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