Chapter 13 regulation of gene expression Flashcards
(19 cards)
What is an operon?
A group of genes in bacteria that are controlled together. (Operates genes all at once)
What is the function of an operator?
-DNA switch for gene expression
-Repressor binds here to turn genes OFF
-blocks RNA polymerase if occupied
What does a regulatory gene do?
It makes a protein (like a repressor) that controls other genes.
What is a repressor?
A protein that blocks gene expression by binding to the operator.
What is the promoter in gene regulation?
The starting point where RNA polymerase binds to begin transcription.
What are structural genes?
Genes that code for proteins needed for a function.
What’s the difference between a repressible and inducible operon?
Repressible = usually ON, can be turned OFF (ex: trp operon).
Inducible = usually OFF, can be turned ON (ex: lac operon).
What is the trp operon?
A gene system in bacteria that makes tryptophan when it’s needed.
What is the lac operon?
A gene system in bacteria that helps break down lactose when it’s present.
How does chromatin structure affect gene expression?
Tightly packed DNA (heterochromatin) is hard to read; loosely packed (euchromatin) is easier to read.
What is a gene mutation?
A change in the DNA sequence.
How can mutations cause cancer?
They can turn proto-oncogenes into oncogenes or damage tumor suppressor genes, causing uncontrolled cell growth.
What is an oncogene?
A mutated gene that causes cancer by making cells divide too much.
What is a tumor suppressor gene?
A gene that normally stops cells from dividing too much.
What is the structure and function of an operon?
In prokaryotes: promoter + operator + genes.
Controls gene expression.
How are the trp and lac operons regulated?
Trp = repressible (off when tryptophan present). Lac = inducible (on when lactose present).
Difference between repressible and inducible operons?
Repressible = normally on, turned off. Inducible = normally off, turned on.
How does chromatin structure affect gene expression?
Tightly packed = off (heterochromatin). Loosely packed = on (euchromatin).
How do mutations cause cancer?
Mutations in proto-oncogenes or tumor suppressors = uncontrolled cell growth.
