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

Activator: Complete epigenome survey

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

Specialized cells of the body develop from stem cells

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

Determination gives rise to related cell populations in a body

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.

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?

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

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

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

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.

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

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?