RNA stands for ribonucleic acid; the critical, chemical "middle-man" for translating genetic information.

Like DNA, RNA consists of a backbone of sugar and phosphate fused to a sequence of bases. Unlike DNA, which has deoxy-ribose in its backbone, the sugar in RNA's backbone is ribose. In addition, the base T (thymine) in DNA is replaced by U (uracil) in RNA.

One of the most important differences between DNA and RNA is that RNA exists only a single strand rather than as a double helix. RNA mediates the expression of genetic information permantly stored in DNA.

There are three major kinds of RNA:

• Messenger RNA (mRNA): transports the genetic information to the ribosomes, which are the sites of protein synthesis
• Ribosomal RNA (rRNA): a major structural component of ribosomes
• Transfer RNA (tRNA): mediates the recruitment and linking of individual amino acids into the growing protein chain at ribosomes.