Mitosis Cell Division Copyright Pearson Prentice Hall Why

Mitosis- Cell Division Copyright Pearson Prentice Hall

Why do cells divide by Mitosis? • Growth &Repair • Reproduction of single celled organisms • Maintenance constant environment Amobea Reproducing

Cells dividing by Mitosis……. Skin • Identical to original cell • Same chromosome # • Identical chromosome makeup

The Cell Cycle • The sequence of growth and division of a cell. • 95% of cell cycle in interphase • 5% of cell cycle in mitosis

Events of the Cell Cycle Mitosis Copyright Pearson Prentice Hall

Interphase “Intermission” • Growth Stage 1 (G 1) – During G 1 phase • The cell increases in size • The cell synthesizes new proteins and organelles • Normal metabolic activity of the cell

Interphase “Intermission” • Synthesis Stage (S) During the S phase, • metabolic activity of the cell continues • chromosomes are replicated • DNA synthesis takes place Once a cell enters the S phase, it usually completes the rest of the cell cycle.

Interphase “Intermission” • Growth Stage 2 (G 2) – The G 2 Phase (Second Gap Phase) • metabolic activity of the cell, prepare for division • organelles and molecules required for cell division are produced Once G 2 is complete, the cell is ready to start the M phase—Mitosis

Interphase • “Intermission” • Normal metabolic activities • Major state • DNA= chromatin

Where is DNA located? 1. Nucleus 2. Chromosomes DNA

Duplicated Chromosome (Late Interphase): Sister Chromatids Centromere

Stages of Mitotic Cell Division • Prophase • Metaphase • Anaphase • Telophase • “ 1 st” • “middle” • “apart” • “far” or separate

Section 10 -2 Mitosis Spindle forming Prophase Chromosomes (paired Centromere Copyright Pearson Prentice Hall chromatids)

Prophase • Nuclear membrane disappears • Doubled DNA = condensed now called “chromosomes” • Spindle fibers

Spindle forming – Prophase • Prophase is the first and longest phase of mitosis. • The centrioles separate and take up positions on opposite sides of the nucleus. • Spindle fibres form Centromere Copyright Pearson Prentice Hall Chromosomes (paired chromatids)

Mitosis Centriole Spindle Centriole Metaphase Copyright Pearson Prentice Hall

Metaphase • Chromosomes line up mid- cell

Centriole – Metaphase • The second phase of mitosis is metaphase. • The chromosomes line up across the center of the cell. • Microtubules connect the centromere of each chromosome to the poles of the spindle. Spindle Copyright Pearson Prentice Hall

Mitosis Individual chromosomes Anaphase Copyright Pearson Prentice Hall

Anaphase • Chromosomes move to opposite poles at • Centrioles in animals • Spindle apparatus in plants

Spindle & spindle fibers: Pull apart the sister chromatids Spindle fibers

– Anaphase Individual • Anaphase is the third chromosomes phase of mitosis. • The sister chromatids separate into individual chromosomes. • The chromosomes continue to move until they have separated into two groups. Copyright Pearson Prentice Hall

Mitosis Nuclear envelope reforming Telophase Copyright Pearson Prentice Hall

Telophase • Cells divide • Cell plate or membranes form • Nucleus reappears

– Telophase Mitosis • Telophase is the fourth and final phase of mitosis. • Chromosomes gather at opposite ends of the cell and lose their distinct shape. • A new nuclear envelope forms around each cluster of chromosomes Copyright Pearson Prentice Hall

Cytokinesis Copyright Pearson Prentice Hall

Cytokinesis: cell’s cytoplasm divides & splits apart

Returns to Interphase • “Intermission” • Normal metabolic activities • Major state • DNA=chromatin

Plant versus Animal Mitosis Plant: • Cell wall • cell plate in telophase • Spindles Animal: • No cell wall • membrane cytokinesis • Centrioles

Animal Telophase Interphase

Text Reference • 2. 5 pages 40 -44 • Q #1 -5 page 44