Brain PopBrain Pop

When something When something divides, what divides, what happens to it?happens to it?

MitosisMitosis

Cell Division: MitosisCell Division: MitosisDividing cellsDividing cells

Mitosis and the cell Mitosis and the cell cyclecycle

4 main stages of mitosis4 main stages of mitosis A. ProphaseA. Prophase B. MetaphaseB. Metaphase C. AnaphaseC. Anaphase D. TelophaseD. Telophase

Prokaryotic Cell DivisionProkaryotic Cell Division•Bacterial cells reproduce by Binary Fission•No Nucleus

•Much simpler process than in eukaryotic organisms (why?)

Prokaryotic (Single) Cell Prokaryotic (Single) Cell DivisionDivision

1.1. Begins with Begins with DNA replication DNA replication (why?); (why?);

2.2. Followed by Followed by elongation of elongation of cellcell, and separation between , and separation between the two halves. the two halves.

3.3. Results in Results in two new cells two new cells that that are identical (clones) of are identical (clones) of original cellsoriginal cells

Eukaryotic (has nucleus) Eukaryotic (has nucleus) Cell DivisionCell Division

11. . Mitosis…cells Mitosis…cells Grow or replace dead or Grow or replace dead or worn out cells, or to worn out cells, or to repair woundsrepair wounds

Any cell but sex cells Any cell but sex cells

sperm & egg)sperm & egg)

DNA and Cell DivisionDNA and Cell Division

During cell division, the During cell division, the genetic material DNA, genetic material DNA, needs to be copied and needs to be copied and divided evenly between divided evenly between the two new cellsthe two new cells

Eukaryotic Chromosome Eukaryotic Chromosome StructureStructure

DNA in cells is divided DNA in cells is divided into long chains called into long chains called chromosomeschromosomes (CZ) (CZ) (“volumes” of DNA)(“volumes” of DNA)

During mitosis, chromosomes fold During mitosis, chromosomes fold up and condense up and condense

Eukaryotic Eukaryotic ChromosomesChromosomes

Chromosomes Chromosomes must be must be replicated replicated before cell division.before cell division.

Sister chromatidsSister chromatids: :  two identical copies (chromatids) formed by the replication of a single chromosome

Chromosome structureChromosome structure At the start of mitosis they At the start of mitosis they

condense & take a form condense & take a form The replicated chromosomes The replicated chromosomes

stay together and are called stay together and are called sister chromatidssister chromatids

Sister chromatids are Sister chromatids are attached at the attached at the centromere.centromere.

The Cell Cycle: (1) The Cell Cycle: (1) InterphaseInterphase

When a cell is dividing When a cell is dividing and is building its and is building its

chromosomes, then it chromosomes, then it is said to be in is said to be in InterphaseInterphase

III. Stages of mitosisIII. Stages of mitosis

The Spindle FibersThe Spindle Fibers

Moves chromosomes Moves chromosomes during mitosisduring mitosis

In both plant and animal In both plant and animal cells, spindle fibers cells, spindle fibers originate from originate from centrosomescentrosomes; in animal ; in animal cells, from cells, from centriolescentrioles

(2) Prophase(2) Prophase Chromosomes Chromosomes

continue to continue to condensecondense

Centrioles move Centrioles move to each pole of to each pole of the cell the cell

Spindle fibers are Spindle fibers are assembledassembled

Nuclear envelope Nuclear envelope dissolvesdissolves

(3) Metaphase(3) Metaphase Microtubules pull Microtubules pull

the chromosomes the chromosomes to align them at to align them at the the center center of the of the cellcell

Metaphase plateMetaphase plate: : imaginary path imaginary path through the center through the center of the cell where of the cell where the chromosomes the chromosomes lineline

(4) Anaphase(4) Anaphase

The The centromeres centromeres separateseparate

Spindle fibers Spindle fibers pull sister pull sister chromatids chromatids apart toward apart toward the polesthe poles

(5) Telophase(5) Telophase Spindle fibers Spindle fibers

disassemblesdisassembles Nuclear membrane Nuclear membrane

forms around each forms around each set of sister set of sister chromatidschromatids

Chromosomes begin Chromosomes begin to uncoilto uncoil

Nucleolus reappears Nucleolus reappears in each new nucleusin each new nucleus

(6) Cytokinesis(6) Cytokinesis

Usually occurs between Usually occurs between late anaphase and end of late anaphase and end of telophasetelophase

Two mechanisms Two mechanisms

1.1. Cell plate formation Cell plate formation (plants)(plants)

2.2. Cleavage (animals)Cleavage (animals)

Cytokinesis: Animal CellCytokinesis: Animal Cell

Cytokinesis: Plant CellsCytokinesis: Plant Cells