We have already learned that a genetic code exists
that stores information in the form of triplet
nucleotides in DNA, and that this information
is initially expressed through the process of transcription
into a messenger RNA that is complementary to one strand
of the DNA helix. However, the final product of gene
expression, in almost all instances, is a polypeptide chain
consisting of a linear series of amino acids whose
sequence has been prescribed by the genetic code. In this
chapter we will examine how the information present in
mRNA is processed to create polypeptides, which then
fold into protein molecules. We also review the evidence
that confirms that proteins are the end products of genes
and briefly discuss the various levels of protein structure,
diversity, and function. This information extends our
understanding of gene expression, and provides an important
foundation for interpreting how the mutations that
arise in DNA can result in the diverse phenotypic effects
observed in organisms.
- 14.1 Translation of mRNA Depends on Ribosomes
and Transfer RNAs
- Ribosomal Structure
- tRNA Structure
- Charging tRNA
- 14.2 Translation of mRNA Can Be Divided into Three
Steps
- Initiation
- Elongation
- Termination
- Polyribosomes
- 14.3 Crystallographic Analysis Has Revealed Many
Details About the Functional Prokaryotic
Ribosome
- 14.4 Translation Is More Complex in Eukaryotes
- 14.5 The Initial Insight That Proteins Are Important
in Heredity Was Provided by the Study of Inborn
Errors of Metabolism
- 14.6 Studies of Neurospora Led to the One-Gene:
One-Enzyme Hypothesis
- Beadle and Tatum: Neurospora Mutants
- Genes and Enzymes: Analysis of Biochemical
Pathways
- 14.7 Studies of Human Hemoglobin Established That
One Gene Encodes One Polypeptide
- 14.8 The Nucleotide Sequence of a Gene and the
Amino Acid Sequence of the Corresponding
Protein Exhibit Colinearity
- 14.9 Protein Structure Is the Basis of Biological
Diversity
- 14.10 Posttranslational Modification Alters the Final
Protein Product
- 14.11 Protein Function Is Directly Related to the
Structure of the Molecule
- 14.12 Proteins Consist of Functional Domains
