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In Sections 14 and 15, we saw how genetic information is replicated and transcribed. We will complete our examination of the central dogma by investigating the last leg: protein synthesis, or translation. Protein synthesis is called translation because it is the biochemical process that translates nucleic acid information into amino-acid-sequence information. The genetic code is the Rosetta stone of the translation process, a code that correlates a sequence of three nucleotide bases, called a codon, with a particular amino acid. Translation is a crucial step in the central dogma because proteins perform virtually all biochemical functions, including the synthesis of DNA and RNA.

Befitting its position linking the nucleic acid and protein languages, the process of protein synthesis depends critically on both nucleic acid and protein factors. Protein synthesis takes place on ribosomes—enormous complexes containing three large RNA molecules and more than 50 proteins. Interestingly, the ribosome is a ribozyme; that is, the RNA components play the most fundamental roles.

Transfer RNA molecules, messenger RNA, and many proteins participate in protein synthesis along with ribosomes. The link between amino acids and nucleic acids is first made by enzymes called aminoacyl-tRNA synthetases. By specifically linking a particular amino acid to each tRNA, these enzymes perform the translation. Indeed, the enzymes that catalyze this crucial reaction are the actual translators of the genetic code.

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We begin our examination of translation by first investigating the code that links the nucleic acid alphabet to the amino acid alphabet. Next, we will study some of the key players in the process of translation. We complete our study of translation by learning how all of the components cooperate to orchestrate protein synthesis in an accurate and controlled fashion.

In the final chapter of this section, and of the textbook itself, we complete our examination of the techniques of biochemistry, a task that we began in Chapter 5, with an investigation of recombinant DNA technology. Although only two chapters explore the tools of biochemistry, all that we have learned, and all that future students of biochemistry will learn, is knowledge revealed by the creative use of techniques like those that we examined in Chapter 5 and will examine in Chapter 41.

✓ By the end of this section, you should be able to: