1. LEQ: How do cells become committed to specialized functions in bodies?
Key terms – stem cell, cell determination,
Reading – 28.1, 5.5, 8.6 (eukaryotic gene regulation)
Lab due 5/3
Test/note cards Friday 5/4

2. Activator:
Complete epigenome survey

3. Stem cells add new cells to a body when they divide
Stem cells have the ability to
divide and renew themselves via mitosis
Stochastic (top)
Asymmetric (bottom)
Daughter cells can specialize in biological tasks

4. Specialized cells of the body develop from stem cells

5. A stem cell divides and forms specialized populations of cells
Cell Determination is committing to become one cell type.
Factors affecting determination:
Cell position in the body
Signaling
Gene expression

6. Determination gives rise to related cell populations in a body

7. The use of stem cells has biomedical applications
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

8. Summary:
What are the characteristics of stem cells?
Explain how a stem cell’s fate is “determined,” what factors influence the future jobs these cells will perform?
Discuss the potential to use stem cells in medical therapy
Is using human embryos essential for medical therapy? Why or why not?

9. Chromosomes are imprinted with epigenetic marks
The epigenome is a pattern of chemical modifications on chromatin that control gene expression
Imprinting involves placing epigenetic marks on chromosomes
Sex cell formation
Goal: single gene expression for certain genes that direct development & metabolism
Male vs. female
Diploidy is essential

10. Changes to the epigenome alter how cells use their DNA
Histone modifications – chemically modify “tails”
DNA methylation – CpG islands: CG rich DNA

11. Epigenetic marks impart a genetic memory on cells “determining” their fate
Genes can be switched on or off permanently

12. Changes in epigenetics can result in disease
(A) previously unmethylated tumor suppressor gene such as p53 becomes methylated suppressing gene expression
(B) A protooncogene is demethylated, allowing TFs express the protein product.

13. Epigenetic marks can change over time
Development
Cell differentiation
Imprinting
Chromosomes can be permanently tagged
Reversible
Age correlation
Disease correlation

14. Summary:
A cell has undergone determination to become an endocrine gland cell. If it is transplanted to a leg muscle, what do you think will happen to this cell?