Mitosis

Why Mitosis?  The purpose of mitosis is to generate two new cells from one cell.  The “daughter cells” generated are exact copies of the “parent cell”  Mitosis is happening in many cells in your body as we speak!  Some cells divide more frequently than others

Mitosis is part of the Cell Cycle Interphase Mitosis Cytokinesis

Key Events in the Cell Cycle  The cell gets larger  Organelles are made  Genetic information is duplicated  Half of the DNA and organelles go to one end and the other half to the opposite end  The cell is split down the middle to make 2 new cells Interphase

Interphase  Gap1 (G1)  Preparation for growth  Organelles, membranes, and ribosomes made  Synthesis (S)  Chromosomes replicated  Gap2 (G2)  Preparation for division  Mitochondria divide  Remember, mitochondria have their own chromosome! Mitosis Cytokinesis G1 G2 S Q4 Part 1

Key Events in the Cell Cycle  The cell gets larger  Organelles are made  Genetic information is duplicated  Half of the DNA and organelles go to one end and the other half to the opposite end  The cell is split down the middle to make 2 new cells Interphase Mitosis Q7

Chromosomes in Somatic Cells Nucleus of cell during G1 Chromosomes not duplicated Nucleus of cell after S phase Chromosomes are duplicated Nucleus of cell after mitosis Chromosomes are not duplicated Homologous pair

Keep in Mind…

Mitosis  Prophase  Metaphase  Anaphase  Telophase Interphase A Cytokinesis P M T

Prophase  Pro =forward, forth  Chromosomes condense  Nuclear envelope breaks down  Membrane surrounding the nucleus  Centrioles move to opposite poles  Spindle fibers grow Q4 Part 2

Metaphase  Meta =after, with  Chromosomes line up at the midline  Spindle attaches to chromosomes at the centromere  The centromere is where the sister chromatids are attached chromatids are attached Q4 Part 2

Anaphase  Ana =against  Centromeres split  Sister chromatids are pulled to opposite poles by the shortening of spindle fibers  Once separated, each sister chromatid is now a chromosome (and each is exactly like the chromosome found in the original cell before S of interphase) Q4 Part 2

Telophase  Telo =completion of a goal  Spindle breaks down  Nuclear envelope forms in each of the daughter cells  Chromosomes decondense Q4 Part 2

Key Events in the Cell Cycle  The cell gets larger  Organelles are made  Genetic information is duplicated  Half of the DNA and organelles go to one end and the other half to the opposite end  The cell is split down the middle to make 2 new cells Interphase Mitosis Q7 Cytokinesis

Cytokinesis  “Cell-making” phase  Organelles and cytoplasm are distributed between daughter cells  Microfilament band at equator contracts to pinch apart 2 new daughter cells Interphase Cytokinesis Mitosis

Summary of Cell Cycle  Cell grows  DNA replicates  Organelles are made  Chromosomes condense  Chromosomes line up at the equator  Replicated chromosomes are pulled apart to opposite poles  Chromosomes decondense  Two daughter cells are formed G1 S G2 Prophase Metaphase Anaphase Telophase Cytokinesis

I A C P M T I P ee on the MAT, See?

GoGoGoGo  Resting phase  Cell may:  Enter S phase  Die  Cell is damaged  Do nothing  Neuron GoGo Cell Death Sit tight Mitosis Cytokinesis G1 G2 S

Cell Cycle Checkpoints Mitosis Cytokinesis G1 G2 S DNA damage checkpoints Spindle checkpoint

Apoptosis  Programmed cell death  Neat and orderly

Necrosis  Cell explodes  Not so neat and orderly  In response to injury

Telomeres  Consist of a repeated sequence of DNA of DNA  Nature’s solution to the end-replication problem  Very tips of chromosomes cannot be replicated  Shortened with each mitotic division  Limits # of possible cell divisions  Cell will not divide after ~50 divisions  Not found in eggs/sperm, bone marrow cells, cancer cells  Shortening is hastened by chronic stress

Cell Differentiation  The process whereby a cell becomes specialized  Every cell contains the exact same genetic information (all 23 chromosome pairs)  One chromosome from mom and one from dad  Not all genetic info is being used by every cell  Different cell types are making different proteins different proteins  The proteins being made by a cell give it specialized characteristics give it specialized characteristics (e.g. blood cell vs. brain cell) (e.g. blood cell vs. brain cell)

Stem Cells  Important for regenerating cells that are lost (e.g. skin cells) and for growth  Stem cells are undifferentiated  Totipotent =able give rise to any cell type  Progenitor cells  Somewhat specialized  Pluripotent =able to produce many different cell types different cell types

Pathways to Cell Specialization  Each specialized cell type uses only certain “recipes” from the “cookbook”

Embryonic Stem Cells -IVF  Yields totipotent cells  Uses frozen embryos from in vitro fertilization  in vitro =in a dish  in vivo =in the body

Embryonic Stem Cells – Nuclear Transfection

Cloning

Adult Stem Cells  Pluripotent  Found in bone marrow, umbilical cord blood, certain parts of the brain Even I have stem cells!