Translation and genetic code
Objectives
By the end of this module, you should be able to:
- Describe the levels of organization of protein structure and recognize that the amino acid sequence influences protein structure.
- Describe the stages of translation (initiation, elongation, and termination).
- Identify the location of signal sequences necessary for translation (Shine-Dalgarno/ribosome binding sequence, start codon, stop codon) within DNA or RNA sequence.
- Find an open reading frame within a sequence of DNA or RNA and predict the polypeptide sequence encoded by an RNA or DNA.
- Define the following terms: codon, anticodon, ribosome, tRNA, N-terminus, C-terminus, amino acid, polypeptide, Shine-Dalgarno sequence, large subunit, small subunit, start codon, stop codon, open reading frame.
Introduction
Translation is the process of protein synthesis. In many ways, proteins can be thought of as the molecular workers of a cell. Proteins are used as structural components of the cell, to import and export materials from the cell, to metabolize nutrients, to build macromolecules, to communicate with other cells, to perform DNA replication and transcription, and for many other purposes. Nearly every cellular function requires the action of proteins.
Proteins are polymeric macromolecules assembled from amino acid subunits, per instructions encoded in genes. In the Transcription module, we saw how the cell transcribes genes into RNA. In this module, we will look at how the large multicomponent ribosomes translate mRNA (messenger RNA) to synthesize proteins. This requires tRNAs (transfer RNA) that act as adaptors, carrying amino acids into the ribosome to match the mRNA sequence, as well as additional protein factors.
This module includes the following sections:
- An overview of protein structure
- A comparison of the prokaryotic and eukaryotic ribosomes
- A look at the genetic code and the structure of tRNAs
- A description of the steps of translation, including initiation, elongation, and termination.
- A review of gene structure, with elements required for both transcription and translation
