25 terms

mastering bio ch.18

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operon
not in eukaryotic organisms
- group of closely linked bacterial genes
3 structural genes in the operon
lac Y
lac A
lac Z
Lac Z
encodes enzyme
lac A
role in lactose metanbolism
lac Y
encodes proteins
RNA polymerase
binds to promoters in the bacteria and transcribes the coding regions of the genes
allosteric regulation
a small molecule binds to a large protein and causes the protein to change shape and activity
when glucose is absent
lactose levels are high
lacl gene
expressed regardless of the presence of lactose
enzyme b-galactose
cleaves lactose into glucose and galactose
adenylyl cyclase
enzyme
converts ATP to cAMP
Jacob & Monod
proposed the operon model
what happens when Lactose binds to lac repressor
its inactivated by causing it to change shape
allosteric
what is not apart of the operon
regulatory genes
regulatory gene
codes for a protein
it controls the transcription of another gene
what do regulatory genes bind to
the operator
operon not transcribed
tryptophan present
lactose absent
operon transcribed but not sped up
tryptophan absent
lactose present
glucose present
operon transcribed quickly through a positive control
lactose present, glucose absent
inducer
taken up by a cell
binds to the repressor so that the repressor is no longer binding to the operator
lactose operon is likely to be transcribed
when the cyclic AMP and lactose levels are both high within the cell
activators
transcription factors
bind to enhancers
not composed of DNA sequence
enhancer
can function thousands of nucleotides away from the promoter and the transcription start site
proteasome
enzyme complex that break down protein
for a repressible operon to be transcribed, what must happen
RNA polymerase must bind to the promoter
- the repressor must be inactive