CCHS AP Biology Goldberg Chapter 16 Regulation of Gene Expression Some of the BIG Questions… How are genes turned on & off? How do cells in a multicellular organism, all with the same genes, differentiate to perform completely different, specialized functions in eukaryotes? But first… Bacterial Metabolism Bacteria need to respond quickly to changes in their environment ex. if have enough of a product, need to stop production why? waste of energy to produce more how? stop production of anabolic enzymes ex. if find new food/energy source, need to utilize it quickly why? metabolism, growth, reproduction how? start production of catabolic enzymes Reminder: Regulation of Metabolism One way: Feedback inhibition product acts as an allosteric inhibitor of 1 st enzyme in synthesis pathway = inhibition - Another Way to Regulate Metabolism Another way: Gene regulation block transcription of genes for all enzymes in synthesis pathway saves energy by not wasting it on unnecessary protein synthesis = inhibition - Gene Regulation in Bacteria Control of gene expression enables individual bacteria to adjust their metabolism to environmental change Cells vary amount of specific enzymes by regulating gene transcription turn genes on or turn genes off ex. if you have enough of something in your cell then you don’t need to make enzymes used to build more of that thing it’s a waste of energy! turn off genes which codes for enzymes
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CCHS AP Biology Goldberg
Chapter 16
Regulation of Gene
Expression
Some of the BIG Questions…
How are genes turned on & off?
How do cells in a multicellular organism,
all with the same genes, differentiate to
perform completely different, specialized
functions in eukaryotes?
But first…
Bacterial Metabolism
Bacteria need to respond quickly to
changes in their environment
ex. if have enough of a product,
need to stop production
why? waste of energy to produce more
how? stop production of anabolic enzymes
ex. if find new food/energy source,
need to utilize it quickly
why? metabolism, growth, reproduction
how? start production of catabolic enzymes
Reminder: Regulation of Metabolism
One way: Feedback inhibition
product acts
as an allosteric
inhibitor of
1st enzyme in
synthesis
pathway
= inhibition-
Another Way to Regulate Metabolism
Another way: Gene regulation
block transcription of genes for all enzymes in synthesis pathway saves energy by
not wasting it on unnecessary protein synthesis
= inhibition-
Gene Regulation in Bacteria
Control of gene expression enables
individual bacteria to adjust their
metabolism to environmental change
Cells vary amount of specific enzymes
by regulating gene transcription
turn genes on or turn genes off
ex. if you have enough of something in your
cell then you don’t need to make enzymes
used to build more of that thing
it’s a waste of energy!
turn off genes which codes for enzymes
CCHS AP Biology Goldberg
Genes Grouped Together
Operon genes grouped together with related functions
ex. enzymes in a certain metabolic pathway
promoter = RNA polymerase binding site single promoter controls transcription of all
genes in operon
transcribed as 1 unit & a single mRNA is made
operator = DNA binding site of regulator protein
So how can genes be turned off?
First step in protein production?
transcription
stop RNA polymerase!
Repressor protein
binds to DNA near promoter region
blocking RNA polymerase
binds to operator site on DNA
blocks transcription
operatorpromoter
Repressor Protein Model
DNATATA
RNApolymerase
repressor
repressor repressor protein
Operon: The operator, promoter & genes they control