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11/18/16 The Cell Cycle and Mitosis Notes Page ___ Biology is the only subject in which multiplication is the same thing as division… THE CELL CYCLE • Series of events that cells go through as they grow and divide • Consists of four phases: – G1 PHASE – CELL GROWTH – S PHASE – CHROMOSOME REPLICATION – G2 PHASE – PREPARATION FOR MITOSIS – M PHASE – MITOSIS AND CYTOKINESIS Cell Cycle: order does matter! • Remember: Cell Cycle phases as IPMAT • I= Interphase (G1, S, G2 phases) • P= Prophase (M phase) • M= Metaphase (M phase) • A= Anaphase (M phase) • T= Telophase (M phase) MITOSIS: Making New Body Cells Making New DNA 1 11/18/16 Where it all began… And now look at you… You started as a cell smaller than a period at the end of a sentence… How did you get from there to here? Getting from there to here… • Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide… Why do cells divide… " One-celled organisms # # for reproduction asexual reproduction (clones) amoeba " Multi-celled organisms # for growth & development # for repair & replacement " from fertilized egg to adult starfish " replace cells that die from normal wear & tear or from injury 2 11/18/16 Dividing cells… Copying DNA • What has to be copied • A dividing cell duplicates its DNA – DNA – organelles – cell membrane – lots of other molecules – creates 2 copies of all DNA – separates the 2 copies to opposite ends of the cell – splits into 2 daughter cells DNA • enzymes cell plant cell animal cell nucleus Organizing & packaging DNA " But the DNA starts loosely wound in the nucleus " If you tried to divide it like that, it could tangle & break Chromosomes of Human Female DNA 46 chromosomes 23 pairs cell nucleus DNA has been wound up DNA in chromosomes in everyday working cell cell nucleus 4 chromosomes in this organism DNA in chromosomes in cell getting ready to divide 3 11/18/16 Chromosomes of Human Male double-stranded human chromosomes ready for mitosis 46 chromosomes 23 pairs MITOSIS=body cells DNA must be duplicated… chromosomes in cell DNA in chromosomes cell nucleus • Asexual reproduction for single cells (remember: My toe needs to grow; this does not need a partner !) 4 single-stranded chromosomes • Growth & development for multicellular organisms • Four phases of Mitosis: (Hint: PMAT) 1st P= Prophase duplicated chromosomes duplicated chromosomes cell 2nd M= Metaphase 3rd A= Anaphase 4th T= Telophase 4 double-stranded chromosomes nucleus 4 11/18/16 Mitosis: Dividing DNA & cells • Stage 2: DNA winds into chromosomes • Stage 1: cell copies DNA – DNA is wound up into chromosomes to keep it organized Copy DNA! DNA Mitosis: Dividing DNA & cells duplicated chromosomes Wind up! cell cell nucleus (prophase) Cells spend the most time in Interphase nucleus (interphase) Mitosis: Dividing DNA & cells • Stage 3: Chromosomes line up – chromosomes line up in middle – attached to protein cables that will help them move Line up! duplicated chromosomes lined up in middle of cell (metaphase) Mitosis: Dividing DNA & cells • Stage 4: Chromosomes separate – chromosomes split, separating pairs – start moving to opposite ends Separate! chromosomes split & move to opposite ends (pull apart) (anaphase) 5 11/18/16 Mitosis: Dividing DNA & cells • Stage 5: Cell starts to divide Mitosis: Dividing DNA & cells • Stage 6: DNA unwinds again – cells start to divide – nucleus forms again – cells separate – now they can do their every day jobs Divide! Makes 2 new cells (telophase) New daughter cells Bye Bye! (cytokinesis) Cell division in Animals • Get 2 exact copies of original cells – same DNA – clones 6 11/18/16 Mitosis in whitefish embryo Mitosis in plant cell Overview of mitosis interphase I.P.M.A.T.C. prophase Please Make Another Two Cells cytokinesis metaphase anaphase telophase 7 11/18/16 REGULATING THE CELL CYCLE • REGULATORY PROTEINS (Cyclins) – CONTROL CELL GROWTH – STIMULATES THE CELL TO PRODUCE SPINDLE AND BEGIN CELL DIVISION – NORMAL CELLS STOP GROWING WHEN THEY COME INTO CONTACT WITH EACH OTHER What happens when there is Cancer Cells? • Cancer Cells – Don t respond to signals that control the cell cycle – Do not stop dividing – Can form tumors • Carcinogens – Damage DNA, results in cancer – Radiation – Cigarette smoke – Environmental chemicals 8