Gene Expression

Key Notes

What You Will Learn

• Gene expression and its regulation

• Role of regulatory proteins in gene expression

What is Gene Expression?

• Gene expression is the process of using a gene to produce a protein

• All cells have the same genes but express different ones to perform specific functions

• This allows cells to specialize and respond to changes

Why is Gene Expression Regulated?

• Ensures correct proteins are made at the right time and place

• Prevents wasteful protein production

• Allows cells to adapt to developmental, environmental, or physiological changes

Stages Where Gene Expression is Regulated

1. Chromatin modification – DNA is chemically or structurally altered

2. Transcription – The main stage where gene expression is controlled

3. Translation – Regulation of protein synthesis

4. Post-transcriptional modification – Processing of mRNA before translation

5. RNA transport – Regulation of mRNA movement within the cell

6. mRNA degradation – Controlling mRNA lifespan to influence protein production

7. Post-translational modifications – Proteins are modified after synthesis for proper function

Regulatory Proteins and Transcription Control

• Regulatory proteins (transcription factors) bind to DNA and control transcription

• Types of regulatory proteins:

  • Activators: Enhance transcription by helping RNA polymerase bind to the promoter

  • Repressors: Inhibit transcription by blocking RNA polymerase

• Other mechanisms influencing transcription:

  • Basal factors: Help RNA polymerase position at the gene start

  • Enhancers: DNA regions that help loop DNA to bring activators closer to the transcription complex

  • Mutations in regulatory regions can turn genes permanently on or off, causing problems

Summary

• Gene expression is regulated to ensure proteins are made when needed

• Regulatory proteins control transcription by binding to DNA

• Activators increase transcription, while repressors decrease it

Review Questions

1. What is gene expression?

2. Why is gene expression regulated?

3. List three stages where gene expression is regulated.

4. Describe how regulatory proteins regulate gene expression.

5. Compare activators to repressors.