1. Promoter sequences from 10 bacteriophage and bacterial genes

5. Figure 10-13 Catabolite control of the lac operon. (a) Only
under conditions of low glucose is adenylate cyclase active
and cAMP (cyclic adenosine monophosphate) formed.
(b) When cAMP is present, it forms a complex with CAP
(catabolite activator protein) that activates transcription by
binding to a region within the lac promoter.

7. NEGATIVE REGULATION THE trp OPERON X Aporepressor Operator
REPRESSIBLE TRANSCRIPTION
THE trp OPERON
Aporepressor
Operator
Co-repressor
Active repressor X

12. 1 2 3 4

13. RNA Polymerase Transcribing a Prokaryotic Gene
Initiation occurs at a transcription start site in a promoter (DNA sequence)
Termination occurs at a transcription stop site
Activation of bacterial RNA polymerase requires binding of sigma factor

14. Transcription in Eukaryotes
Eukaryotic RNA Polymerases
Three different RNA polymerases transcribe nuclear genes
Other RNA polymerases found in mitochondria and chloroplasts

15. Eukaryotic vs. Prokaryotic Transcription
In eukaryotes, transcription and translation occur in separate compartments.
In bacteria, mRNA is polycistronic; in eukaryotes, mRNA is usually monocistronic.
Polycistronic: one mRNA codes for more than one polypeptide
moncistronic: one mRNA codes for only one polypeptide
3 RNA polymerases in euk., 1 in prok.
Binding of Basal Transcription Factors required for euk. RNA Pol II binding.
“Processing” of mRNA in eukaryotes, no processing in prokaryotes

20. Gene expression

22. TERMINATION RNA polymerase meets the terminator
Terminator sequence: AAUAAA
RNA polymerase releases from DNA
Prokaryotes-releases at termination signal
Eukaryotes-releases base pairs after termination signal