Mitosis EQ: What is the result of cell reproduction? 2007-2008 1 1 1

Biology is the only subject in which multiplication is the same thing as division… 2007-2008 2 2 2

Overview of mitosis I.P.M.A.T. interphase prophase (pro-metaphase) cytokinesis metaphase anaphase telophase 3 3 3

What is Mitosis? 1) Process of eukaryotic cell reproduction Parent Cell 1) Process of eukaryotic cell reproduction 2) Nucleus divides to form 2 separate, identical nuclei DNA condenses into chromosomes Chromosomes align in center Have students look at the pictures and try to figure out what is happening to the DNA in each. The slide is animated so you can ask the questions and reveal the answers when you are ready Chromosomes separate DNA uncoils; cytoplasm divides 4 4

Organizing DNA DNA is organized in chromosomes ACTGGTCAGGCAATGTC DNA Organizing DNA DNA is organized in chromosomes DNA wrapped around proteins DNA-protein complex = chromatin histones chromatin double stranded chromosome 5 5 5

double-stranded mitotic human chromosomes 6 6 6

Mitotic Chromosome After DNA replication: 2 sister chromatids narrow at centromeres contain identical copies of original DNA homologous chromosomes homologous chromosomes Centromeres are segments of DNA which have long series of tandem repeats = 100,000s of bases long. The sequence of the repeated bases is quite variable. It has proven difficult to sequence. sister chromatids single-stranded homologous = “same information” double-stranded 7 7 7

Time to divide & multiply! Interphase 90% of cell life cycle (G1, S, G2) cell doing its “everyday job” produce RNA, synthesize proteins/enzymes prepares for duplication if triggered I’m working here! Time to divide & multiply! 9 9 9

Interphase Nucleus well-defined Prepares for mitosis DNA loosely packed in long chromatin fibers Prepares for mitosis replicates chromosomes produces proteins & organelles 10 10 10

Mitosis Dividing cell’s DNA between 2 daughter nuclei 4 phases (PMAT) “dance of the chromosomes” 4 phases (PMAT) prophase metaphase anaphase telophase 11 11 11

Why does a cell spend the majority of its life in Interphase? Table Discussion Why does a cell spend the majority of its life in Interphase?

green = key features Prophase Chromatin condenses into visible chromosomes called chromatids Centrioles move to opposite poles of cell Spindle fibers start to stretch across the cell Nuclear membrane breaks down 13 13 13

Metaphase Chromosomes align along middle of cell (metaphase plate) green = key features Metaphase Chromosomes align along middle of cell (metaphase plate) 14 14 14

green = key features Anaphase Sister chromatids separate apart to become individual chromosomes move to opposite poles 15 15 15

Telophase Chromosomes arrive at opposite poles New nuclei form Cell cleavage visible 16 16 16

Cytokinesis Cytoplasm splits, creating two new daughter cells Animal cells: Cleavage is seen (indention in cell membrane) Plant cells: Cell plate formation occurs Division of cytoplasm happens quickly. 17 17 17

Cytokinesis the final stage of eukaryotic cell reproduction/division The cytoplasm divides: Animal cells: Cleavage is seen (indention in cell membrane) Plant cells: Cell plate formation occurs Cytokinesis almost always follows mitosis. This is what creates two separate cells. Ask students what would happen if you have mitosis without cytokinesis (one cell with two nuclei). 18 18

How is mitosis different from cytokinesis? Table Discussion How is mitosis different from cytokinesis?

Mitosis in animal cells 20 20 20

Mitosis in Plant Cell

Mitosis in plant cell 22 22 22

onion root tip 23 23 23