MITOSIS!

Lets Ponder

How many cells do we have in our bodies? Approx. 100 trillion cells!! WOWZA!

What would happen if our arms and/or legs consisted of just one giant cell and that cell stopped working or died? We wouldn’t have a working limb, or it may

fall off!

Pondering Cont’d

What do we do if our cells die or get damaged? Buy some on ebay? Amazon.ca? Nope, we let this process called mitosis do its

thing So why do we need Mitosis?

To fill the space left by dead cells (cell reproduction), to help cells grow (cell growth), and to pass on cell DNA

What is this “Mitosis” thing?

Well......? Yes, you’re right! It is an asexual cellular division that produces

two identical daughter cells How does this exciting process happen?

Right again! It begins with a process called interphase Followed by Mitosis Finally following mitosis cytokinesis occurs

Stages of Interphase

G0 Non-dividing stage

G1 (Gap 1): Produce RNA Synthesis protein

S Phase DNA replicates One sister chromosome becomes two sister

chromatids G2 (Gap 2):

Cells prepare for mitosis

Stages of Mitosis

Prophase Metaphase

http://www.youtube.com/watch?v=C6hn3sA0ip0

Anaphase Telophase

Prophase

What characteristics are present, when prophase begins?

1. Individual condensed chromosomes become visible

2. Condensation continues through prophase3. Nucleolus disappears

Prophase cont’d

Assembling the Spindle Apparatus Microtubule apparatus made of spindle fibers

continues to assemble Animal cells form an arrangement called an

aster Linking sister chromatids to opposite

poles Second group of microtubules grow out from

centromeres to poles Sister chromatids won’t separate if both

connected to same pole

MetaphaseKey Characteristics of Metaphase.1. Stage begins when chromosomes align in center of the cell2. Alignment occurs along the metaphase plate

a. Not a physical structureb. Indicates where future axis of cell division occurs

3. Centromeres are equidistant from each pole

Metaphase cont’d Centromeres divide at the end of metaphase

Centromere splits in two, freeing sister chromatids from one another Spindle fibres attach to the kinetochore,

which controls/supervises movements of chromosomes during cell division

All centromeres divide in synchrony

Anaphase

Is the shortest phase, during which sisterchromatids separate Chromatid drawn to poleto which its kinetochore is attached Separation achieved by two simultaneous

microtubular actions Poles move apart Centromeres move toward poles

Telophase

Separation of chromatidsCompletes partitioning of replicating genome

Spindle apparatus is disassembled Tubulin units of microtubules are used to build

new cytoskeleton Nuclear envelope re-forms around each new

set of chromosomes Chromosomes begin to uncoil to allow gene

expression Nucleolus reappears

The Last 3 Steps

Cytokinesis

Mitosis complete at end oftelophase Replicated genome divided

into two nuclei at oppositeends of cell

Cytoplasmic organellesassort to regions that will become separated

Cleavage of the cell into twohalves constitutes cytokinesis

Cytokinesis in animal cells Cell is pinched in two by a constricting belt of microfilaments

Actin filaments slide past one another Produces distinct cleavage furrow around circumference of cell

Furrow deepens until the cell is pinched in two