BELLRINGER 11/03 What is Mitosis? 2. List the 4 Mitotic Phases? Clue: Purple Monkeys Attack Tokyo YOU NEED YOUR NOTEBOOKS! Reminders: HW, Lab Fee, Grades and Midterm this Thursday!

CELL GROWTH & REPRODUCTION

Why do cells divide? Why can’t we just be one giant cell? Small cells are more efficient Cells must be small Small cells have a greater Surface Area-to-Volume Ratio When cells get too big, their surface area is not large enough for oxygen, food, and wastes to diffuse across The cell would starve to death or be poisoned from waste

Cell Reproduction Vocab Chromosomes = condensed DNA, they form when cell is ready to divide Made up of 2 halves held together in the center by the centromere Chromatin= a form of chromosomes that look like loose, unorganized spaghetti (this is what we see in Interphase) Sister chromatids- exact copies of a chromosome held together by a centromere (this is what we see in the S phase when DNA is copied)

Cell Cycle Cell Cycle = sequence of growth & division of a cell 1. Interphase 2. Cell Division Mitosis Cytokinesis Interphase = growth period, majority of a cell’s life G1: Cells grow and makes proteins (enzymes) S: Chromosomes containing DNA are copied G2: Cell prepares for division

Mitosis Mitosis = period of cell division, 2 daughter cells get formed in the end, each with its own nucleus with identical chromosomes Divided into 4 Phases PMAT

1. Prophase Chromatin thickens and coils into visible chromosomes (2 sister chromatids) Nuclear Envelope & Nucleolus break down Centrioles at opposite ends of cell start sending out Spindle Fibers between them

2. Metaphase Chromosomes line up in the center of the cell Spindle Fibers attach to the centromere of each of the sister chromatids and pulls them in the middle

3. Anaphase Separation of Sister Chromatids to the opposite ends (poles) of the cell Centromeres split

4. Telophase Chromatids pulled to opposite ends of the cell ends Nuclear Envelope & Nucleolus re-form Chromosomes appear as chromatin again Mitosis ends New daughter cells have identical DNA

Cytokinesis Cytokinesis = division of the cytoplasm Cleavage (pinch) in animals Cell Plate (new wall) in plants