Genetic elements

The genetic elements that control gene expression

Transcriptional control

Translational control

inducer, operator, promoter, effector, repressor, activator, cis-acting, trans-acting, constitutive synthesis,attenuation

Jacob and Monod’s Operone Model

Operon; collections of adjacent genes that are transcribed into single mRNA molecules

; a group of genes coordinately regulated“operational unit” of gene expression

How bacteria could rapidly produce an enzymatic activity in response to the external chemical?

Transcriptional control

Two styles of transcriptional control of lac operon

Two general categories of regulation

• Negative control: repressor protein present which prevents transcription, inducer (usually a small molecule) is needed to allow initiation of transcription.

• Positive control: activator protein induces transcription.

cis-acting elementtrans-acting

Lac repressor bound operator

The repressor molecule has two important sites, one that binds to the DNA (operator) and the other that binds to the inducer.

Question: if mutation occurred DNA binding domain, what phenotype would the bacteria show?

How about the mutation in inducer binding domain?

Positive regulation: CAP(catabolite activator protein)

Attenuation

Charles Yanofsky,

E.coli tryptophan operon

E.coli tryptophan opern

trpL; two tryptophan codon (UGG)

A model for attenuation for tryptophan operon

Translational control

Hairpin structure of binding sites on 16S rRNA and r-protein mRNAFor the ribosomal protein S8Regions of homology are indicated in orage

Synthesis and translation of prokaryotic vs. eukaryotic mRNA