Genes and Proteins
15.2 The Genetic Code
The Central Dogma: DNA Encodes RNA; RNA Encodes Protein
The Central Dogma describes the flow of genetic information from DNA to RNA to protein.
15.3 Prokaryotic Transcription
The genetic code is a degenerate, non-overlapping set of 64 codons that encodes for 20 amino acids and 3 stop codons.
Initiation of Transcription in Prokaryotes
RNA polymerase initiates transcription at specific DNA sequences called promoters.
Elongation and Termination in Prokaryotes
Transcription elongation begins with the release of the polymerase σ subunit and terminates via the rho protein or via a stable hairpin.
15.4 Eukaryotic Transcription
Initiation of Transcription in Eukaryotes
Initiation is the first step of eukaryotic transcription and requires RNAP and several transcription factors to proceed.
Eukaryotic Elongation and Termination
Elongation synthesizes pre-mRNA in a 5' to 3' direction, and termination occurs once RNAPII encounters a poly-A tail.
15.5 RNA Processing in Eukaryotes
Eukaryotic pre-mRNA receives a 5' cap and a 3' poly-A tail before introns are removed and the mRNA is considered ready for translation.
Processing of tRNAs and rRNAs
rRNA and tRNA are structural molecules that aid in protein synthesis but are not themselves translated into protein.
15.6 Ribosomes and Protein Synthesis
The Protein Synthesis Machinery
Protein synthesis, or translation of mRNA into protein, occurs with the help of ribosomes, tRNAs, and aminoacyl tRNA synthetases.
The Mechanism of Protein Synthesis
Protein synthesis involves building a peptide chain using tRNAs to add amino acids and mRNA as a blueprint for the specific sequence.
Protein Folding, Modification, and Targeting
In order to function, proteins must fold into the correct three-dimensional shape, and be targeted to the correct part of the cell.