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Lecture

Chapter 12 Textbook Notes
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Department
Biology
Course
BIOL 102
Professor
Daniel Lefebvre
Semester
Fall

Description
Gene regulation occurs, so that energy and resources can be conserved, by only expressing certain genes during a specific situation or condition Constitutive genes /”Housekeeping genes”– expressed continuously; needed for survival of organism Small effector molecules – binds to a regulatory transcription factor (repressor or activator) and causes a conformational change in the protein; in many cases, its effect determines whether or not the protein can bind to DNA Repressors and activators have two domains: 1. one site at which the protein binds to the DNA 2. Binding site for the small effector molecule Polycistronic mRNA – an mRNA that encodes more than one protein Operon – structural gene cluster Lac operon – contains the genes for the enzymes needed to allow it to metabolize lactose - contains promoter, lacP, that is used to transcribe the structural genes: lacZ, lacy and lacA - inducible operon - regulated by repressor protein (negative control) and the catabolite activator protein (CAP) (positive control)  CAP is controlled by a small effector molecule: cyclic AMP, or cAMP CAP site – DNA sequence recognized by an activator protein Operator/lacO site – a sequence of nucleotides that provides a binding site for a repressor protein Lacl gene – encodes for lac repressor (important for regulation of the lac operon) Francois Jacob and Jacques Monod (1950’s) – first researchers to investigate genetic regulation Inducer – small effector molecule that increases that rate of transcription Trp operon (of E. coli) – encodes enzymes that are required to make amino acid, Tryptophan (building block of cellular proteins) Small effector molecules on the lac operon and the trp operon: - lac repressor binds to operator in the absence of its small effector molecule - trp repressor binds to operator in the only presence of its small effector molecule Combinatorial control – the phenomenon that many factors determine the expression of any given gene Eukaryotic structural genes that encodes proteins, three features are found in Forms most promoters: core 1. Transcriptional start site promoter 2. TATA box – important for determining the transcription starting point 3. Response elements Basal transcription factors/GTF’s -
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