Outline 10C – Mitosis & Cytokinesis 2/27/2019 Outline 10C – Mitosis & Cytokinesis 2/27/2019

I. Chromatid Movements A. During mitosis, chromatids on each chromosome are physically moved. B. Spindles 1. Made up of centrioles (animals only) & the microtubule fibers 2. The whole region is called the centrosome & it will help to organize the movement of chromosomes 2/27/2019

1. Centriole pairs replicate during G2 C. Forming the Spindle 1. Centriole pairs replicate during G2 2. At beginning of mitosis the pairs of centrioles move to opposite sides of cell 3. Spindle fibers form as they move 4. Microtubule fibers of spindle attach to the centromeres of the chromosomes 2/27/2019

Spindle Forming Centriole (Animals only) Chromosomes

D. Separating Chromatids 1. Microtubules start to “reel in” the chromatids, dragging them to opposite poles of the cell 2. Once the two chromatids separate from each other, they are considered to be individual chromosomes. ***HINT: Count chromosomes by counting the # of centromeres 2/27/2019

Chromatids Separating

II. Mitosis A. Division of nucleus into two nuclei, each with a complete set of chromosomes B. Consists of 4 phases: 1. Prophase a. Chromosomes become visible b. Nuclear envelope disappears c. Spindle forms 2/27/2019

Prophase Chromosomes

a. Chromosomes line up at the equator of cell b. Spindle fibers attach 2. Metaphase a. Chromosomes line up at the equator of cell b. Spindle fibers attach 2/27/2019

b. Sister chromatids move to opposite poles 3. Anaphase a. Centromeres divide b. Sister chromatids move to opposite poles Individual chromosomes – single stranded 2/27/2019

a. Nuclear envelope reforms b. Chromosomes uncoil 4. Telophase a. Nuclear envelope reforms b. Chromosomes uncoil c. Spindle disappears 2/27/2019

III. Cytokinesis A. Cytoplasm divides in half, forming two separate cells B. Different in animals from plants: 1. Animal cell membrane pinched in half by belt of proteins 2. Plant cells need to grow a new wall: a. Vesicles from Golgi fuse at midline & form a cell plate that grows to divide the cell 2/27/2019

Animal Cell Cytokinesis

Plant Cell Cytokinesis

IV. End Results A. Two daughter cells about equal in size B. Each new cell has: 1. A complete set of chromosomes that are identical to original cell’s 2. Half of the original cell’s cytoplasm & organelles 2/27/2019

IV. Mitosis Video If link doesn’t work, click on this icon on desktop 2/27/2019