DNA struc­ture

APC Australia - - Feature » Computing With A Double Helix -

Each strand of the dou­ble helix of a DNA mod­ule is formed of molec­u­lar groups called nu­cleo­tides. A nu­cleo­tide is a com­bi­na­tion of three smaller types of mol­e­cules: a su­gar, one or more phos­phate groups and a ni­troge­nous base. There are four types of bases called Ade­nine (A), Thymine (T), Gua­nine (G) and Cy­to­sine (C), and the nu­cleo­tides con­tain­ing th­ese bases can ap­pear in any or­der along a strand of DNA. While the nu­cleo­tides are bonded to­gether with strong chem­i­cal bonds in a strand, the bases can also bond to other bases via a weaker so-called hy­dro­gen bond, link­ing the two stands. Th­ese wind around each other to form a dou­ble helix. ‘A’ will only bond with its com­ple­men­tary base’ T’, and ‘C’ will only bond with ‘G’ — so for ev­ery ‘A’ in one strand there is an ad­ja­cent ‘C ‘in the other strand. Shown here is a seg­mentof DNA straight­ened for clar­ity.

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