lecture 7 ProkaryoticTranscription

Question 1

Learning Outcomes

Answer 1

*Define the key terms used in molecular biology located in the glossary.

*Describewhyelements in the promoter are important to enabling transcription.

*Explain the effect transcription factors can have on therecruitment of the RNA polymerase holoenzyme

Question 2

what are RNA polymerase “Holoenzyme”

Answer 2

IncludesRNA polymerase and sigma factors.

Without the sigma factor the RNA polymerase cannot bind to the DNA and progress from the promoter.

Question 3

Gene expression in Prokaryotes

Answer 3

*Polycistronic mRNAs generated from a set of genes which make up an operon.

*Usually proteins/enzymes involved in regulation of a process.

*Cis-regulatory regions and operator regions control initiation of transcription

Question 4

Activators of Expression

Answer 4

▪Cis-regulatory sequences in promoter (& enhancer) bind protein.

▪Trans-regulatory factors (i.e. transcription factors)

▪Control recruitment of accessory factors to RNA polymerase and therefore control initiation of transcription

Question 5

what are Repressors of transcription

Answer 5

Binding to the repressor to a ligand enables binding to the operator region and then displaces initiation complexes containing RNA polymerase

Question 6

what are Operons: clever controls

Answer 6

oBinding of repressor prevents RNA polymerase recruitment.

oBinding of the activator to its ligand allows binding to the cis-regulatory region of the promoter.

oBinding of activator to the cis-regulatory region recruits RNA polymerase to “turn on” transcription

Question 7

Summary

Answer 7

*Prokaryotic genomes are more simple partially due to polycistronic mRNAs.

*Prokaryotes have less “non-coding” DNA and less elaborate control of gene transcription.

*Common features of Eukaryotic and Prokaryotic gene control mechanisms include:
*Consensus sequences
*Transcription factors (trans-activators)
*Ability to inhibit transcription with binding of repressors