Chapter 15
Genes and Proteins
By Boundless
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The genetic code is a degenerate, non-overlapping set of 64 codons that encodes for 21 amino acids and 3 stop codons.
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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.
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Initiation is the first step of eukaryotic transcription and requires RNAP and several transcription factors to proceed.
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Elongation synthesizes pre-mRNA in a 5' to 3' direction, and termination occurs in response to termination sequences and signals.
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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.
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rRNA and tRNA are structural molecules that aid in protein synthesis but are not themselves translated into protein.
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Protein synthesis, or translation of mRNA into protein, occurs with the help of ribosomes, tRNAs, and aminoacyl tRNA synthetases.
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Protein synthesis involves building a peptide chain using tRNAs to add amino acids and mRNA as a blueprint for the specific sequence.
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In order to function, proteins must fold into the correct three-dimensional shape, and be targeted to the correct part of the cell.