Figure 1.2. Structure of base-paired, double-stranded DNA.

Figure 1.2

Structure of base-paired, double-stranded DNA. Each strand of DNA consists of a backbone of 5-carbon deoxyribose sugars connected to each other through phosphate bonds. Note that as one follows the sequence down the left-hand strand (A to C to G to T), one is also following the carbons of the deoxyribose ring, going from the 5´ carbon to the 3´ carbon. This is the basis for the 5´ to 3´ directionality of DNA. The 1´ carbon of each deoxyribose is substituted with a purine or pyrimidine base. In double-stranded DNA, bases face each other in the center of the molecule and base-pair via hydrogen bonds (dotted lines). Base-pairing is specific so that adenine pairs with thymine, and guanine pairs with cytosine.

From: Chapter 1, Molecular Biology

Cover of Holland-Frei Cancer Medicine
Holland-Frei Cancer Medicine. 5th edition.
Bast RC Jr, Kufe DW, Pollock RE, et al., editors.
Hamilton (ON): BC Decker; 2000.
© 2000, BC Decker Inc.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.