chapter 17 transcription and translation from gene to protein
TRANSCRIPT
Chapter 17
Transcription and Translation
From Gene to Protein
Overview
The “recipe” for a protein is encoded within the DNA
One gene, one protein
Recipe for one protein is copied into a working version in the form of RNA (Transcription)
Recipe in RNA is used to make a protein (Translation)
Two Steps Required for Gene Expression
TranscriptionPolymerization of RNA molecule from DNA template strandOne gene one transcript
TranslationProduction of a protein molecule based on the instructions contained within a mRNA molecule
Transcription
Components
Promotor
TATA box
RNA Polymerase
RNA nucleotides
Termination sequence
Steps in Transcription
Initiation
Elongation
Termination
Transcription Initiation
Transcription factors bind to TATA box
RNA Polymerase joins transcription factors
DNA strands opened
RNA nucleotides aligned
Transcription Elongation
Initiation factors remain at promotorRNA Polymerase catalyzes building of RNA molecule5’-3’ direction of formation of RNAContinues until termination signal is reached
Transcription Termination
RNA Polymerase reaches the termination signalSnap backRhoComplex destabilizationRelease of all componentsDNA closes
Movies of Transcription
Transcription
Post Transcriptional ModificationEukaryotes only
3’ end- poly A tail
5’ end methylated guanine cap
Exons
Introns
Splicing
Splicosome
Mature mRNA
Post transcriptional Modifications
Splicing
Types of RNA
r RNA - Pol I
m RNA – Pol II
t RNA – Pol III
Translation
Manufacture of protein from information in mRNA
Components Involved in Translation
Messenger RNA
RibosomeA slot
P slot
E slot
Transfer RNA
Amino acids
Terms
Codon
Anticodon
Gene
Chromosome
Genome
Steps found in Translation
Initiation
Elongation
Termination
Initiation of Translation
5’ end of mRNAStart codonAUGSmall sub unit of the ribosomeInitiation tRNAMethionineLarge sub unit of ribosomeA slotP slotE slot
Elongation of Translation
New A.A. bearing tRNA enters the A slot
A.A. transferred from P slot onto AA in A slot
Ribosome slides over one codon
Continues until a stop codon enters the A slot
Termination of Translation
Stop codon enters the A slot
No tRNA H bonds to stop codon
Release factor enters A slot
Peptide chain hydrolysed from the tRNA in the P slot
Movie of Translation
Translation
Musical version
Recap