Central dogma of genetics.

   Gene  expression  involves transcription of DNA into mRNA, followed by
   translation  of  mRNA  on  a ribosome into a protein, which is made of
   amino acid subunits.

   The translation requires a dictionary, or genetic code.

<LI> RNA is similar to DNA except:
<li> it has Uracil (U) in place of Thymine (T).
+ the   sugar   in   its   nucleotides  is  ribose  instead  of
deoxyribose.