Lecture Notes

Week 1 Notes: Prokaryotic Transcription

Central dogma
 Describes flow of biological information

Introduction
 Transcription is 5’ to 3’ on template that is 3’ to 5’
 Coding strand (non template): DNA strand w/same seq as mRNA (U instead of T) and is related by genetic
code to the prot seq it represents
 RNA pol: enzyme that synthesises RNA using DNA template

Transcription unit
 Promoter: region of DNA where RNA pol binds to initiate transcription
 Startpoint: DNA position corresponding to first base incorporated into RNA (begins at +1)
 Terminator: DNA sequence that causes RNA pol to terminate transcription
 Transcription unit: DNA sequence b/w sites of initiation and termination by RNA pol
o May include more than one gene

Prokaryotic transcription Eukaryotic transcription




Transcription occurs by base pairing in a ‘bubble’ of unpaired DNA
 RNA pol separates both strands in a transient (temporary) ‘bubble’
o Uses one strand as template for direct synthesis of complementary RNA seq
 ‘Bubble’ length is 12-14 bp ; RNA-DNA hybrid length is 8-9 bp

RNA polymerisation
 3’-OH group of the last ribonucleotide added to the chain reacts with an incoming ribonucleotide 5’
triphosphate
 rNTP: ribonucleoside w/3 phosphates, building blocks of RNA synthesis & primers in DNA replication

Transcription: 3 stages
 Initiation:
o RNA pol binds to promoter on DNA to form closed complex