Chapter 15
Genes and Proteins
By Boundless
![Thumbnail](../../../../../figures.boundless-cdn.com/29881/square/genetic code table with sec pyl.jpg)
The genetic code is a degenerate, non-overlapping set of 64 codons that encodes for 21 amino acids and 3 stop codons.
![Thumbnail](../../../../../figures.boundless-cdn.com/18974/square/figure-15-02-01.jpeg)
RNA polymerase initiates transcription at specific DNA sequences called promoters.
Transcription elongation begins with the release of the polymerase σ subunit and terminates via the rho protein or via a stable hairpin.
![Thumbnail](../../../../../figures.boundless-cdn.com/18977/square/figure-15-03-01.jpeg)
Initiation is the first step of eukaryotic transcription and requires RNAP and several transcription factors to proceed.
![Thumbnail](../../../../../figures.boundless-cdn.com/29907/square/transcription with fact.jpg)
Elongation synthesizes pre-mRNA in a 5' to 3' direction, and termination occurs in response to termination sequences and signals.
![Thumbnail](../../../../../figures.boundless-cdn.com/20425/square/5-27-cap-structure.jpg)
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.
![Thumbnail](../../../../../figures.boundless-cdn.com/18981/square/figure-15-04-03.jpeg)
rRNA and tRNA are structural molecules that aid in protein synthesis but are not themselves translated into protein.
![Thumbnail](../../../../../figures.boundless-cdn.com/2877/square/peptide-syn.jpg)
Protein synthesis, or translation of mRNA into protein, occurs with the help of ribosomes, tRNAs, and aminoacyl tRNA synthetases.
![Thumbnail](../../../../../figures.boundless-cdn.com/30142/square/eukaryotic translation initiation.jpg)
Protein synthesis involves building a peptide chain using tRNAs to add amino acids and mRNA as a blueprint for the specific sequence.
![Thumbnail](../../../../../figures.boundless-cdn.com/20346/square/protein-folding.jpg)
In order to function, proteins must fold into the correct three-dimensional shape, and be targeted to the correct part of the cell.