Lac Operon (13.3) Flashcards
(30 cards)
Gene expression
process that heritable information in a gene is made into a function gene product, such as protein or RNA
Gene regulation
the process of controlling gene expression. The mechanisms of gene regulation can occur during any part of gene expression
This includes transcription, RNA processing, translation or post-translational modifications
What molecules are involved in gene regulation?
Activators, inducers, repressors, co-repressors, operators, and regulatory sequences
Regulated promoters
promoters that allow for transcription only when certain conditions are met
How many promoters are found at the lac operon?
One: one promoter controls expression of LacZ, LacY and LacA
Why do organisms regulate gene expression?
Different organs and tissues need different proteins
Different genes are needed under different environmental conditions
Transcripts and proteins take up space
Constitutive gene expression
expressed all the time, at constant levels
In the lac operon, which of the following is constituively expressed?
lacl (encoding the lac repressor)
What are some genes that an organism might want to always be expressed?
RNA polymerase, ATPase, Ribosomes, RNAs, Histone, tRNAs, DNA repair enzymes, Oxphos complexes, Cell cycle enzymes and Proteosome
What are 3 ways to regulation gene activity?
transcriptional, translational and post-transitional
Operator
DNA sequence region that lac repressor can bind to
lactose, no glucose
Transcription levels
Bound or unbound: CAP and LacR
high levels of transcription
CAP: bound
LacR: unbound
lactose and glucose
Transcription Levels
Bound or unbound: CAP and LacR
medium transription
CAP: unbound
LacR: unbound
no lactose, no glucose
Transcription Levels
Bound or unbound: CAP and LacR
No transcription
CAP: bound
Lacr: bound
No lactose, glucose
No transcription
CAP: unbound
Lacr: bound
When CAP binds to CAP site, what happens?
RNA polymerase is recruited to the promoter region
What kind of regulation is Catabolite Activating Protein?
postive regulation
Negative regulation
When binding of regulatory protein to DNA blocks transcription
Positive regulation
When binding of a regulatory protein to DNA activates transcription
Activator
regulatory protein that promotes gene expression
Repressor
regulatory protein that prevented gene expression
The lac repressor binds to
the operator sequence and blocks transcription of the lac operon
The lac repressor is inactivated by what molecule?
Allolactose
Inducer
a small molecule that promotes gene expression
