Cell division

How one cell becomes two

Mitosis + Cytokinesis = Cell division• Most cells in all eukaryotic organisms will divide

many times throughout the life of the organism – _______________ is the process by which a cell

duplicates its genetic materials (chromosomes and prepares for cell division

– ________________ is the division of the rest of the cell into two separate but identical daughter cells

– ______________________________________________________________________________________________________________________________

• In animals, cell division occurs during embryonic development, growth, and wound healing

• Errors during cell division can cause cell death or cancer

Mitosis reorganizes DNA in the cell

• __________________________________________________________________________________________________________________

• During mitosis, the two copies are reorganized, repackaged into two sets of chromosomes, and divided to opposite ends of the cell

• In most organisms, ___________________________________________________________________________________________________________________(the cell body dividing in two)

• The original cell (mother cell) is identical to the two resulting cells (daughter cells)

Mitosis vocabulary• Nucleus – location of DNA inside the cell• Nuclear envelope – the membrane that separates the nucleus from the cytoplasm• DNA – an incredibly long molecule that contains genetic blue prints for cell behavior• Chromatin – a loosely bundled coil of DNA. Most of the time, DNA is organized in

this form, “ a loose rope”• Histones – proteins which hold a DNA strand together in the form of chromatin• Chromosome – a highly organized form of chromatin, “a tightly wrapped and carefully

knotted rope ”– Each chromosome is composed of two identical parts called chromatids– Chromatids: two halves of a chromosome which contain the same genetic information – DNA exists in the form of chromosomes only during mitosis– Each chromosome looks like an X

• Centromere – a bundle of proteins which connects the two chromatids of a chromosome, the “knot at the center of the X“

• Microtubules – part of a cell’s cytoskeleton. These are tubes of protein which use to pull chromosomes apart and to opposite ends of a cell during mitosis. They are powered by ATP!

• Mitotic spindle – How microtubules are organized during mitosis. This is a collection of microtubule fibers which is formed to coordinate the pulling of apart of chromosomes.

• Metaphase plate – the line along which chromosomes are lined up during mitosis. This arrangement is coordinated by the mitotic spindle.

Chromosome Structure

5 Phases of Mitosis

• Mitosis is composed of five phases– ___________________– ___________________– ___________________– ___________________– ___________________

• During each phase, different proteins in the cell perform specific roles to divide the two copies of genetic material

• ___________________________________________________________________________________________________________________________

Prophase

• ________________________________________________________________________ into chromosomes inside the nucleus

• Microtubules are organized into _____________________ in the cytoplasm

• Nuclear envelope is dissolving• By the end of prophase

– Chromosomes and mitotic spindle are fully organized

– Nuclear envelope has disappeared

Prometaphase

• Chromosomes move towards each other and into the center of the cell

• Microtubules move into the nuclear region and begin to connect to chromosomes

• ________________________________________________________________________________

Metaphase

• The mitotic spindle is fully organized, and has pulling the chromosomes to the center of the cell

• The spindle aligns chromosomes so that each centromere is lined up along the metaphase plate (the center of the cell)

Anaphase

• ____________________________________________________________________________________________

• Microtubule fibers contract (___________________), pulling chromatids to opposite ends of the cell towards the two spindles

Telophase

• ____________________________________________________________________________________________________

• New nuclear envelopes begin to form around the chromatin to create two nuclei

• Spindle fibers disperse into the cytoplasm

• The cell membrane begins to cleave in preparation for cytokinesis

Cytokinesis

• The cell membrane is being pinched off to form two separate compartments

• Cytoplasm and organelles are being divided between the two forming cells

• ________________________________________________________________________________________________________________________________________

• Cell division is complete!

Cell division movies

• http://www.youtube.com/watch?v=VlN7K1-9QB0

• http://www.youtube.com/watch?v=CzPGhYiGyZ8&feature=related

• Embryonic division in the worm c.elegans: http://www.youtube.com/watch?v=zsgOl04PESI&NR=1

• http://www.cellsalive.com/mitosis.htm