Reading 8 Flashcards
What is gene regulation?
-Mechanism and systems that control the expression of genes
-key to unicellular flexibility and multicellular specialization
-critical to success of all living organisms
What does it mean to say that a gene is being “expressed” or “not expressed”?
-expressed= gene expression on
-not expressed= gene expression off
What does it mean to say that a gene is “constitutive”?
-expressed continually
What is a regulatory element?
-helps control the expression of the structural genes of the operon by increasing or decreasing their transcription
What is meant by negative control of gene expression?
-regulatory protein is a repressor, binding to DNA and inhibiting transcription
What is meant by positive control of gene expression?
-regulatory protein is an activator, simulating transcription
Prokaryotes, but not eukaryotes, have operons. What is an operon? Draw a diagram of a typical operon
-operon: group of bacterial structural genes that are transcribed together along with their promoter and additional sequences that control their transcription
-regulates expression of genes by controlling transcription
-diagram
What is an operator sequence?
-genetic sequence which allows proteins responsible for transcription to attach to the DNA sequence
-where a repressor can bind and block RNA polymerase action
Is the lac I gene part of the lac operon?
-no
What protein does the lac I gene code for? What does that protein do?
-codes for repressor (R ) protein
-binds to genes promoter region and prevents the production of mRNA
What are the two types of binding sites on the repressor protein?
One for the silencer region and one for the promoter
What happens to the repressor protein when lactose (and thus, allolactose) is present?
allolactose blinds to the repressor protein and makes it inactive
