Biology 100/101
Lecture 16
Control of Gene Expression
(Print Version)

Announcements &

Lecture Objectives

Web Resources

Overview of
Control of
Gene Expression

The Gene

External Control
of Gene Expression

Fat Soluble

Water Soluble

External Environmental

Other Levels
of Control

Lecture Syllabus

IB 100/101 Home Page


Text readings in Hoefnagels

Chapter 3, - Signal Transduction, pg. 56-57
Chapter 8, - Cell Cycle Control and Cancer, pg. 165-170
Chapter 12, - Transcription Factors, pgs 245-246
Chapter 27, Starving a Tumor, pg. 565
Chapter 30, The Endocrine System - Hormones pg. 616-620

You have open access (no log-in or password needed) to instructional materials on the Text web site. Select "Resources" from the upper left of the page and select the text chapter you want.


You may also ask questions and see answers to your classmates' questions in Moodle in the "Talk to Ed" forum.


The content of today's lecture will help you answer question #1 on this assignment:

After studying this material you should be able to:

  1. Explain the concept of gene expression by the process of protein synthesis.

  2. Explain how it has been possible for the somatic cells in all the different parts of your body, given their genetic similarity (give or take a few mutations, of course!), to have developed such different characteristics and functions.

  3. Transcriptional Control of Gene Expression:

    • a. Contrast the roles of the promoter and protein encoding (structural) portions of a gene.

      b. Describe the interactions of the promoter region of a gene, transcription factors, and RNA polymerase in the expression of a gene.

      c. Describe the interactions of water soluble and fat soluble hormones and other extra cellular signals with receptor molecules and transcription factors that "turn on" or "turn off" the expression of a particular gene in a cell.

  4. Compare mechanisms of the control of gene expression involving RNA processing, translation, and protein structure.

  5. Explain how mutation might result in a change in protein structure and function resulting in the loss of control of the expression of a gene.

  6. List some examples of responses to changes in the environment that involve control of gene expression. (One of the qualities shared by all living organisms from Lecture #1.)

Web Resources:

Overview of the Control of Gene Expression

  • All of the living cells in our body have the same genetic information, BUT are able to develop very different structures and functions (skin, nerves, muscles, bone, fat, kidney, etc.).

    • We start our lives as a fertilized egg cell. All the resulting cells are the product of mitosis.

    • All the cells have the same genetic information. (With the exception of random mutations that are not repaired.)

    • Cells develop different structures and functions because different genes are "turned on" or "turned off" in different parts of your body.

    • Cells produce different types and quantities of proteins (gene products).

  • Genes must be turned on or off in the correct sequence during development

    • Control proper embryo developmental sequence: homeotic genes -- during embryo development, genes need to be expressed in a particular sequence within particular groups of cells. One way to accomplish this is to have "master genes" whose products "turn on" a sequence of coordinated events. See Hoefnagels chapter 37, Human Reproduction and Development.

    • Homeotic Genes

    • Body changes are induced by hormones during puberty

  • Organisms respond to the environmental changes by turning on (or off) specific genes or groups of genes.

  • Practical applications:

  • For a more detailed look:

Review of Gene Expression


The Gene Revisited - Promoter and Protein Encoding (structural) Regions

(It had to be more complicated, didn't it?)

A gene consists of two main parts:

External Control of Gene Expression (External to a cell)

Environmental Signals

May be chemical substances or in some cases energy in the form of light.

  • Transcription Factor Proteins are affected directly or indirectly, through Receptor Molecules on the cell surface or within the cell, by interactions with these Environmental Signals.

  • The three dimensional shape and/or the chemical properties of the transcription factor protein are changed by the presence of the environmental signal.

  • The Transcription factor may loose its ability to bind to the DNA of the promoter region and TURN OFF the gene.

  • The transcription factor may gain the ability to bind to the DNA of the promoter region and TURN ON the gene.

  • Long-Term Effects of Drugs On the Brain from National Institutes of Health

  • Information on Common Drugs of Abuse From the National Institute on Drug Abuse.

Light as an Environmental Signal

Environmental Estrogens (EEs)

Other "Levels" of Control of Gene Expression