Updates: Unit 5 Test today! Homework: PreAP reproduction responses due tomorrow Read 5.1, 8.3 Keystone Biology Exam: 5/20, 5/21

LEQ: Why do cells divide? Activator: Sexual reproduction/asexual reproduction Weirdest, most interesting? Key terms: cell cycle

reproduction can result in exponential growth All cells reproduce through a division of a parent cell Exponential growth of a population is possible, but rare Limiting factors Examples?

Asexual reproduction requires no additional individuals Favorable environment Nutrients Result is a genetic clone

Cell Division in Eukaryotes Overview: Division in eukaryotes is managed to coordinate the copying of a large cell with a large amount of DNA Copy the original cell’s DNA (clone); asexual Altering patterns of gene expression allows cells in bodies to specialize

Howard and Pelc demonstrated cell division in bodies The cell cycle is a regular pattern of growth and division displayed by many cells. Gap 1 (G1) DNA synthesis (S) Gap 2 (G2) Mitosis (M)

Many cells in a multicellular organism carry out their lives in G0: normal biological functions as they enter G1 Non-dividing (arrest) Neurons, skeletal muscle

Discussion: Do you think the scientific community should be permitted to conduct research on stem cells? Why or why not? What are the pros/cons, if any?

Summary: Which stages of the cell cycle generally require about the same amount of time in all human cells? During which stage of the cell cycle is the DNA copied? What limits the maximum size of a cell? Speculate: what are the consequences for a tissue/body if cell division proceeds in an unregulated manner? List several thoughts.

Answers: Synthesis (s) S, G2, and M stages The ratio of cell surface area to volume The cells would probably look large and have two nuclei located at opposite sides of the cell.