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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