DNA structure.
<P>
   Each  nucleotide  consists  of a nitrogenous base (T, A, C, or G), the
   sugar deoxyribose, and a phosphate group.
<P>
   The 5' end of the polynucleotide is a phosphate, while the 3' end is a
   hydroxyl group of the sugar.
<P>
   The  phosphate  of one nucleotide forms a covalent bond with the sugar
   of the next, providing a "backbone" from which the bases project.
<P>
   Review:  <A ClAsS=MID Href="../../../med/Vid/Campbell8e/16_Animations/16_07DNADoubleHelix_A.swf" oNClick="popurlt('../../../../med/Vid/Campbell8e/16_Animations/16_07DNADoubleHelix_A.swf');txtcolor('DNAStrand2','gray');return false;" Id=DNAStrand2><iMg sRc="/images/shockwave.gif" aLt='' boRDer=0></A>