Mitosis Review 10292020 SB 2 c 1 Interphase

Mitosis Review 10/29/2020 SB 2 c 1

Interphase • This is where cells spend most of the time • Purpose is cell growth; divided into 3 parts

Interphase: 3 Phases • G 1: cell grows and makes proteins • S: chromosomes doubled so there is enough for two cells – Forms sister chromatids held by a centromere • G 2: cell continues to grow and make proteins

Remember: Mitosis • Purpose is cell division (make 2 cells from one) – Each cell must have its own DNA, cytoplasm, and organelles

Mitosis • There are 4 parts of mitosis – Prophase – Metaphase – Anaphase – Telophase

Prophase • 4 important events – The DNA condenses (chromosome shape) – Nucleus begins to disappear – Centrioles are formed (animals only) • Plants asters are formed – Centrioles send out Spindle Fibers (SF) – Remember P for PREPARATION

Metaphase • 2 important events – Chromosomes line up at the middle of the cell – Spindle fibers connect to the centromere of each sister chromatid – Remember M for METAPHASE and MIDDLE

Anaphase • 3 important events – Centromeres split – Sister chromatids separate to become individual chromosomes – Remember A for ANAPHASE and APART

Telophase • 4 important events – Chromosomes uncoil – Nuclear envelope reforms – Spindle fibers break down – Cytokinesis begins – Remember T for TO THE START

Cytokinesis • The third part of the cell cycle is cytokinesis, or division of the cytoplasm – In animal cells: membrane forms a cleavage furrow and pinches the cell into two – In plant cells: cell plate forms midway between the nuclei

Cytokinesis

Regulating the Cell Cycle • Cyclins: regulate the timing of the cell cycle • Cancer: a disorder in which some of the body’s cells lose the ability to control growth • Cancer cells do not respond to the signals that regulate the growth of most cells 10/29/2020 SB 1 a 12

MEIOSIS REVIEW 10/29/2020 SB 2 c 13

Meiosis • Process of making gametes – Sex cells: Egg and Sperm • Egg Formation = Oogenesis • Sperm Formation = Spermatogenesis • Gametes are haploid 10/29/2020 SB 2 c 14

Phases of Meiosis • Just like mitosis except it occurs twice – No interphase between cytokinesis and the beginning of the next division • This means – no DNA replication 10/29/2020 SB 2 c 15

Results of Meiosis • End up with 4 genetically different haploid cells – In Spermatogenesis – all 4 cells become sperm – In Oogenesis – only 1 of the cells actually becomes the egg, other 3 become polar bodies • Polar bodies help to nourish and protect the egg 10/29/2020 SB 2 c 16

Meiosis I • Start with 1 diploid cell – Prophase I: Crossing over occurs – Metaphase I: Homologous Chromosomes Line up at the equator; Independent assortment – Anaphase I: Chromosomes separates – Telophase I: Chromosomes move to opposite poles – Cytokinesis I: cytoplasm divides • have 2 haploid cells 10/29/2020 SB 2 c 17

Crossing Over 10/29/2020 SB 2 c 18

Review Meiosis I Telophase I Interphase I. Prophase I Metaphase I Anaphase I

Meiosis II • Start with 2 haploid cells – Prophase II: Spindles form, nucleus breaks up – Metaphase II: Chromosomes line up at equator – Anaphase II: Sister chromatids separate – Telophase II: Chromosomes move to opposite poles – Cytokinesis II: Cytoplasm divides • End up with 4 genetically different haploid cells 10/29/2020 SB 2 c 20

Meiosis II Prophase II Meiosis I results in two haploid (n) daughter cells, each with half the number of chromosomes as the parent cell. Metaphase II Anaphase II Telophase II The chromosomes line up on the metaphase plate (or equatorial plate). Sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (n) daughter cells. All are genetically UNIQUE.

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