Although it is DNA (deoxyribonucleic acid) that contains the instructions for directing the synthesis of specific structural and enzymatic proteins, several types of RNA actually carry out the processes required to produce these proteins. These include messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA). Further processing of the various RNA's is carried out by another type of RNA called small nuclear RNA (snRNA). The structure of RNA (ribonucleic acid) is very similar to that of DNA, however, instead of the base thymine, RNA contains the base uracil. In addition, the pentose sugar ribose is missing an oxygen atom at position two in DNA, hence the name deoxy-.

The first step in protein synthesis is the transcription of DNA into mRNA. The mRNA exits the nuclear membrane through special pores and enters the cytoplasm. It then delivers its coded message to tiny protein factories called...