Summary
Gene control involves mechanisms that regulate the expression of genes to ensure that the right genes are expressed at the right time and place. This includes the regulation of structural and regulatory genes, inducible and repressible enzymes, and the use of transcription factors in eukaryotes and operons in prokaryotes.
- Structural Gene — produces a protein that serves a purpose in the cell.
Example: F8 gene for Factor VII. - Regulatory Gene — produces a protein that regulates the expression of other genes.
Example: lacI gene in the lac operon. - Inducible Enzyme — produced only in the presence of a substrate.
Example: Lactase in the lac operon. - Repressible Enzyme — production is stopped by a repressor protein.
Example: Enzymes in amino acid synthesis pathways. - Lac Operon — a group of genes regulated together in prokaryotes.
Example: Controls the production of lactase in bacteria. - Transcription Factor — a protein that binds to DNA to regulate gene transcription.
Example: PIF in plants. - Gibberellin — a plant hormone that promotes enzyme production by affecting gene transcription.
Example: Increases amylase production during seed germination.
Exam Tips
Key Definitions to Remember
- Structural gene
- Regulatory gene
- Inducible enzyme
- Repressible enzyme
- Lac operon
- Transcription factor
- Gibberellin
Common Confusions
- Mixing up structural and regulatory genes
- Confusing inducible and repressible enzymes
- Misunderstanding the role of the lac operon
Typical Exam Questions
- What is the role of a regulatory gene in the lac operon? It produces the lac repressor protein that regulates the operon.
- How does the presence of lactose affect the lac operon? Lactose binds to the repressor, allowing transcription of structural genes.
- What happens when gibberellin is added to a germinating seed? It breaks down DELLA proteins, allowing transcription of the amylase gene.
What Examiners Usually Test
- Differences between inducible and repressible enzymes
- Mechanism of gene regulation in the lac operon
- Role of transcription factors in gene expression