APGRU4L1 Chap 12 Extra Reading Cell Cycle and Mitosis Dr. Ramesh
Biology is the only subject in which multiplication is the same thing as division 2007-2008
The Cell Cycle: Cell Growth, Cell Division 2007-2008
Where it all began You started as a cell smaller than a period at the end of a sentence
And now look at you How did you get from there to here?
Getting from there to here Function of cell division making new cells u continuity of life u asexual reproduction w unicellular organisms growth repair & renew Cell cycle u life of a cell from origin to division into 2 new daughter cells amoeba
Making new cells Nucleus chromosomes u DNA u Cytoskeleton u centrioles in animals u microtubule spindle fibers
Nucleus Function u protects DNA Structure u nuclear envelope double membrane nuclear pores nucleolus DNA histone protein membrane fused in spots to create pores w allows large macromolecules to pass through What kind of molecules need to pass through? chromosome nuclear pore nuclear envelope
Cytoskeleton Function u structural support maintains shape of cell provides anchorage for organelles w protein fibers n u motility cell locomotion cilia, flagella, etc. u regulation microfilaments, intermediate filaments, microtubules organizes structures & activities of cell
Cytoskeleton actin microtubule nuclei
Centrioles Cell division u in animal cells, pair of centrioles organize microtubules spindle fibers u guide chromosomes in mitosis
End of the Tour
Getting the right stuff What is passed on to daughter cells? u exact copy of genetic material = DNA mitosis u division of organelles & cytoplasm cytokinesis chromosomes (stained orange) in kangaroo rat epithelial cell notice cytoskeleton fibers
Overview of mitosis I.P.M.A.T. interphase prophase (pro-metaphase) cytokinesis metaphase anaphase telophase
Interphase 90% of cell life cycle u cell doing its everyday job produce RNA, synthesize proteins/enzymes u prepares for duplication if triggered
Cell cycle Cell has a life cycle G2 Gap 2 M Mitosis G1 Gap 1 cell is formed from a mitotic division S Synthesis G0 Resting cell grows & matures to divide again cell grows & matures to never divide again G 1, S, G 2, M liver cells G 1 G 0 epithelial cells, blood cells, stem cells brain / nerve cells muscle cells
Interphase Divided into 3 phases: u G 1 = 1 st Gap cell doing its everyday job cell grows u S = DNA Synthesis copies chromosomes u G 2 = 2 nd Gap prepares for division cell grows (more) produces organelles, proteins, membranes G 0
Interphase Nucleus well-defined u DNA loosely packed in long chromatin fibers Prepares for mitosis u replicates chromosome DNA & proteins u produces proteins & organelles
Copying / Replicating DNA Synthesis phase of Interphase u dividing cell replicates DNA u must separate DNA copies correctly to 2 daughter cells human cell duplicates ~3 meters DNA each daughter cell gets complete identical copy error rate = ~1 per 100 million bases w 3 billion base pairs in mammalian genome w ~30 errors per cell cycle n mutations (to somatic cells)
Organizing DNA DNA is organized in chromosomes u double helix DNA molecule u wrapped around histone proteins like thread on spools u DNA-protein complex = chromatin organized into long thin fiber u condensed further during mitosis double stranded chromosome ACTGGTCAGGCAATGTC DNA histones chromatin duplicated mitotic chromosome
Copying DNA & packaging it After DNA duplication, chromatin condenses u coiling & folding to make a smaller package DNA mitotic chromosome chromatin
double-stranded mitotic human chromosomes
Mitotic Chromosome Duplicated chromosome u 2 sister chromatids homologous chromosomes u narrow at centromeres u contain identical copies of original DNA homologous chromosomes single-stranded sister chromatids double-stranded homologous = same information
Mitosis Dividing cell s DNA between 2 daughter nuclei u dance of the chromosomes 4 phases u prophase u metaphase u anaphase u telophase
Prophase Chromatin condenses u visible chromosomes chromatids Centrioles move to opposite poles of cell u animal cell Protein fibers cross cell to form mitotic spindle u microtubules actin, myosin u coordinates movement of chromosomes Nucleolus disappears Nuclear membrane breaks down
Transition to Metaphase Prometaphase u spindle fibers attach to centromeres creating kinetochores u microtubules attach at kinetochores connect centromeres to centrioles u chromosomes begin moving
Metaphase Chromosomes align along middle of cell u metaphase plate meta = middle u spindle fibers coordinate movement u helps to ensure chromosomes separate properly so each new nucleus receives only 1 copy of each chromosome
Anaphase Sister chromatids separate at kinetochores u move to opposite poles u pulled at centromeres u pulled by motor proteins walking along microtubules actin, myosin increased production of ATP by mitochondria Poles move farther apart u polar microtubules lengthen
Separation of chromatids In anaphase, proteins holding together sister chromatids are inactivated u separate to become individual chromosomes 1 chromosome 2 chromatids double-stranded 2 chromosomes single-stranded
Chromosome movement Kinetochores use motor proteins that walk chromosome along attached microtubule u microtubule shortens by dismantling at kinetochore (chromosome) end
Telophase Chromosomes arrive at opposite poles u daughter nuclei form u nucleoli form u chromosomes disperse no longer visible under light microscope Spindle fibers disperse Cytokinesis begins u cell division
Cytokinesis Animals u constriction belt of actin microfilaments around equator of cell cleavage furrow forms splits cell in two like tightening a draw string
Cytokinesis in Animals (play Cells Alive movies here) (play Thinkwell movies here)
Mitosis in whitefish blastula
Mitosis in animal cells
Cytokinesis in Plants Plants u cell plate forms vesicles line up at equator w derived from Golgi vesicles fuse to form 2 cell membranes u new cell wall laid down between membranes new cell wall fuses with existing cell wall
Cytokinesis in plant cell
Mitosis in plant cell
onion root tip
Evolution of mitosis Mitosis in eukaryotes likely evolved from binary fission in bacteria u single circular chromosome u no membranebound organelles chromosome: double-stranded DNA Origin of replication replication of DNA elongation of cell ring of proteins cell pinches in two
Evolution of mitosis A possible progression of mechanisms intermediate between binary fission & mitosis seen in modern organisms prokaryotes (bacteria) protists dinoflagellates protists diatoms eukaryotes yeast eukaryotes animals
EXTRA SLIDES to be used for enrichment, but usually do not have time for. 2007-2008
Control of Cell Cycle
Kinetochore Each chromatid has own kinetochore proteins u microtubules attach to kinetochore proteins
Chromosome structure scaffold protein chromatin loop rosettes of chromatin loops chromosome DNA histone nucleosome DNA double helix
Cell Division cycle Phases of a dividing cell s life u interphase cell grows replicates chromosomes metaphase prophase G 2 M anaphase telophase interphase (G 1, S, G 2 phases) mitosis (M) S cytokinesis (C) G 1 produces new organelles, enzymes, membranes G 1, S, G 2 u mitotic phase cell separates & divides chromosomes w mitosis cell divides cytoplasm & organelles w cytokinesis C