Boo-yah Biology! The Cell Cycle Molecular Biology Sumner HS

Cell Reproduction/Division The ability of organisms to reproduce their kind is the one characteristic that best distinguishes living things from nonliving. The continuity of life is based on the reproduction of cells, or cell division.

Analogy Two people sharing taking notes Then get split up to take a test How will you prepare yourself for success

Cell Division Importance Multicellular organisms depend on cell division for Development from a fertilized cell Growth Repair or replacement of “bad” cells

Big Growth We start as one cell We end up being made of trillions of cells They don’t magically appear **Poof!** The result of countless cycles of growth and division of cells.

Question to ponder... What tasks does a cell need to do in order to divide? Have a 2nd copy of DNA Have enough cytoplasm and organelles for a second cell

The Cell Cycle Cells go through predictable, controlled patterns of growth or development and division. Called the cell cycle

The Cell Cycle

Cell 2 Big Picture Interpha se/ Mitosis Cell 1

Cell 2 Big Picture Cont’d Interpha se/ Mitosis Cell 1 Cell 3 Interpha se/ Mitosis Cell 2 Cell 4

Cell Cycle Major Phases Interphase = period of growth, DNA replication and protein synthesis Mitosis = cell division

Interphase Interphase can be divided into subphases G1 phase S phase G2 phase

G1 Phase Rapid growth High metabolic activity Making lots of proteins

S Phase DNA is copied (replicated) Cell has twice the number of normal chromosomes. Cell keeps growing

G2 Phase More proteins made Mitochondria & other organelles replicate Cell keeps growing

Summarize In your own words, summarize each of the phases of interphase.

Mitotic Phase The Mitotic Phase has two major phases Mitosis has four sub-phases Prophase Metaphase Anaphase Telophase Cytokinesis

New Note Instructions For each of the phases of cell division don’t write down the details I put up Instead, prepare to summarize the main events in about 10 words.

Prophase Chromosomes coil up and become visible (twisted rubber band) Centriole begins to form spindle, made from same material as cytoskeleton. Nuclear envelope and nucleolus begin to disappear Summarize!

Metaphase Chromosomes move to “equator” of the cell Each half of the chromosome is attached to a spindle fiber at the centromere. Centromere is a protein that joins the two “sister” chromatids, or replicated chromosome pairs Summarize!

Anaphase Sister chromatids are pulled apart to opposite ends of the cell. Each chromatid is now a separate chromosome. Summarize!

Telophase Genetically identical daughter nuclei form at opposite ends of the cell Nuclear envelope begins to reappear. Summarize!

Cytokinesis In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow. A “string” of cytoskeleton pinches the cell in two Summarize!

Cytokinesis cont. In plant cells, a cell plate forms between the cells after telophase.

Mitosis results in two identical cells called daughter cells Mitosis results in two identical cells called daughter cells

Real Pictures: Early Prophase

Real Pictures: Late Prophase

Real Pictures: Metaphase

Real Pictures: Anaphase

Real Pictures: Early Telophase

Real Pictures: Late Telophase

Test Yourself

Identify prophase, metaphase, anaphase and telophase in these cells. Identify prophase, metaphase, anaphase and telophase in these cells. Check Your Knowledge

Your assignment Fold a piece of paper (to be provided) into 8 sections (1 “hot dog” fold & 2 “hamburger” folds) Draw and label thoroughly each of the 3 stages of interphase, the 4 stages of mitosis & cytokinesis All structures Summary of events Use different colors for the different cell parts and organelles