Base pairing in DNA.
<P>
   The pairs of nitrogenous bases in a DNA double helix are held together
   by hydrogen bonds.
<P>
   The geometry of the bases are the basis of base-pairing rules.
<P>
<BR><LI> Adenine (A) pairs with Thymine (T) by forming two bonds,
<BR><LI> Cytosine (C) pairs with Guanine (G) by forming three bonds.
<P>
   When DNA base-pairs with RNA, A pairs with U.
<P>
   Review:  <A ClAsS=MID Href="../../../med/Vid/Campbell8e/16_Animations/16_05DNAandRNAStructure_A.swf" oNClick="popurlt('../../../../med/Vid/Campbell8e/16_Animations/16_05DNAandRNAStructure_A.swf');txtcolor('base-pairs2','gray');return false;" Id=base-pairs2><iMg sRc="/images/shockwave.gif" aLt='' boRDer=0></A>