ABSTRACT

The sequence of the bases in DNA (our genes) determines the proteins that are produced by various cells (Section M1); however, DNA is not directly involved in protein synthesis. The instructions for protein synthesis are carried out by RNA molecules, which are in three basic categories: messenger (m), transfer (t), and ribosomal (r), giving rise to mRNA, tRNA, and rRNA, respectively. Under the control of RNA polymerases an RNA complement of the DNA template is made. This process is called transcription and results in the formation of mRNA. At a part of the cell called the ribosome, tRNA (carrying an appropriate amino acid) and rRNA follow the instructions of the mRNA to translate the nucleic acid sequence into an amino acid sequence (i.e. a protein).