Download Describe the operon hypothesis and discuss

Describe the operon hypothesis and discuss how it explains the control of
messenger RNA production and the regulation of protein synthesis in
bacterial cells.
STANDARDS:
BACKGROUND:
Max. = 2 points
__ Definition of operon (functionally related genes whose expression is
controlled)
__ DNA consists of genes coding for both structural and regulating proteins
(Hypothesis)
__ Authors of Hypothesis
DESCRIPTION OF OPERON (likely the Lac Operon):
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Max. = 8 points
Structure (diagram)
Max. 4
promoter site
repressor site
operator site
structural genes
inducer
Function
Max. 4
binds RNA polymerase* at 3' site on DNA (* also cAMP-CAP)
produces repressor protein: stops RNA polymerase attaching to promoter
site of attachment of repressor protein
codes for sequential protein
serves to inactivate repressor
CONTROL OF mRNA PRODUCTION & CONSEQUENCES re PROTEIN SYNTHESIS:
__ Inducible model: derepression (lactose example) [gene always off] = 3
points
__ Repressible model: corepression (tryptophan-histidine) [gene always on]
=
3 points
__ CAP model: catabolite induction: with decrease in glucose -> increase in
cAMP
cAMP-CAP binds to promoter site
therefore, transcription -> lactose metabolism = 3 points
(above require explanation & example)
__ Adaptive significance = 2 points
__ Final fate of mRNA transcribed = 2 points
Max. = 5