1. Cell Differentiation and Gene Expression
Activity 17
Cell Differentiation and
Gene Expression

3. Name at least four types of cells that can be found in a human.
How are these cells similar?
How are these cells different?
List student responses on the board. Emphasize that every somatic cell in a human contains the same chromosomes with the same set of genes, but the phenotype—expression of the genes—differs from one type of cell to another. More information and suggestions on holding this class discussion can be found in the Teacher’s Edition for this activity.

4. Read the introduction. Expressed genes are active.
Gene expression is the activity of genes in a cell.

5. Challenge
How does the same set of genes direct the activities of 220 human cell types?

6. Proteins Produced by Four cell types:
Beta cells in the pancreas produce insulin.
Developing red blood cells produce hemoglobin.
Intestinal lining cells produce enzymes that contribute to digestion.
Smooth muscle cells produce actin.
For more information on supporting students as they work through this activity see the Teacher’s Edition for this activity. Make sure students understand what the different paper and binder clips represent in Part B, and that they share their results after they have completed Procedure Step 13.

7. Procedure
For more information on using this literacy strategy with your students see your Teacher’s Edition for this Activity and see Teacher Resources III: Literacy. These guidelines can also be found on Literacy Transparency 3, “Read, Think, and Take Note.”
Students should also fill out the appropriate section of Student Sheet 2.3, “Genetics Case Study Comparison,” after they read the case study. Sample student responses can be found in the Teacher’s Edition for this Activity.

8. Analysis 1 Compare the following in your group’s four cell types:
Chromosomes
Genes
Expression of the genes to produce proteins
Analysis Question 1 asks students to summarize two key points: 1) all cells in the same organism have the same genes and chromosomes, and 2) even through each student started with the same two chromosomes and 11 genes, through selective gene expression, each of the four cells displayed a specific pattern of gene expression and repression. For more information and a sample student response see the Teacher’s Edition for this activity.

9. Analysis 2
What kinds of genes were permanently inactivated in some cells? Why were these genes inactivated?
Analysis Question 2 asks students to summarize a key point: even through each student started with the same two chromosomes and 11 genes, through selective gene expression, each of the four cells displayed a specific pattern of gene expression and repression. For more information and a sample student response see the Teacher’s Edition for this activity.

10. Analysis 5
For your cell explain how gene expression related to the cell’s ability to perform its function in the body.
Analysis Question 5 is a Quick Check of students’ understanding of how gene expression is connected to cell function. For more information and a sample student response see the Teacher’s Edition for this activity and Teacher Resources IV: Assessment.

11. Revisit the Challenge
How does the same set of genes direct the activities of 220 human cell types?
Students should be able to explain how the same set of genes can direct the activity of 220 different human cell types by differential gene expression. See the Teacher’s Edition for this activity for more information and suggestions on holding this class discussion.

12. chromosome expressed (gene) gene expression repressed (gene)
Key Vocabulary
chromosome
expressed (gene)
gene expression
repressed (gene)
transcription factor
See Teacher Resources III: Literacy for more information on key vocabulary and the most effective strategies to enhance student vocabulary learning.
Note that bold words are formally defined in this activity. Words in regular font are used in the activity, but not formally defined. The definition of a key vocabulary word should not be discussed as a class prior to the formal definition being introduced.