Gene Regulation in Prokaryotes and Eukaryotes
Controlling Gene Expression
Why Regulation Is Needed
Cells regulate gene expression to respond to the environment, specialize during development, and conserve energy. Most genes are not expressed constantly.
Prokaryotic vs Eukaryotic Regulation
Prokaryotic
- Often organized in operons
- Transcription and translation can be coupled
- Rapid response to environmental change
Eukaryotic
- Chromatin accessibility matters
- Transcription is separated from translation
- Enhancers and epigenetic control are common
Operons
In prokaryotes, an operon is a cluster of genes regulated together by a single promoter. The lac operon is inducible, while the trp operon is repressible.
Regulatory Logic
Gene regulation is often combinatorial: multiple proteins, DNA elements, and chromatin states work together to determine expression.
Which feature is most associated with eukaryotic gene regulation?
Chromatin state is a major regulatory layer in eukaryotes.
Correct answer: Chromatin modification
What is an operon?
This is common in bacteria.
Correct answer: A set of functionally related genes controlled by one promoter and regulated together.
The lac operon is best described as
The lac operon is turned on in response to lactose, so it is inducible.
Correct answer: Inducible
Epigenetics
Epigenetic regulation includes DNA methylation, histone modifications, and chromatin remodeling. These changes affect expression without changing the DNA sequence.
How can DNA methylation affect gene expression?
Methylation is generally associated with gene silencing.
Correct answer: It often reduces transcription by making DNA less accessible or by recruiting repressive complexes.