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Mitosis Occurs because: –Multi-cellular organisms grow in size and complexity by making more cells –Old and damaged cells are continuously replaced by the division of cells –Single-celled organisms such as bacteria divide to make new, independent organisms Binary fission – asexual reproduction
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Cell Division
Mitosis
Mitosis
• Produces 2 cells – called daughter cells – from one parent cell
• Daughter cells are identical to each another and to the original parent cell
• Most body cells reproduce this way• Similar to binary fission
– Asexual reproduction of organisms without a nucleus
Mitosis
• Occurs because:– Multi-cellular organisms grow in size and
complexity by making more cells– Old and damaged cells are continuously
replaced by the division of cells– Single-celled organisms such as bacteria
divide to make new, independent organisms• Binary fission – asexual reproduction
Mitosis
• The nucleus of the cell divides in two– The nucleus contains
the genetic material – chromosomes – of the organism
• Chromosomes are made of DNA
MitosisThe Cell Cycle
• The nucleus divides in several phases:– Interphase– Prophase– Metaphase– Anaphase– Telophase
MitosisInterphase
• Technically not part of mitosis• A resting phase• DNA (Chromosomes) copies itself exactly
(replicates)• Organelles double in number, to prepare
for division
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
MitosisProphase
• Nuclear membrane disappears • Spindle fibers (or aster fibers) form at the
ends of the cell• Chromosomes coil up and become short
and fat - become visible• Takes about an hour
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
MitosisMetaphase
• Chromosomes in pairs line up along the equator – middle of cell
• Spindle fibers attach to the center of the chromosome pairs – Centromere – the connecting point of the two
chromosomes• Takes about 15 minutes
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
MitosisAnaphase
• Chromosomes divide• Chromatids (half of a chromosome pair)
separate and are pulled to opposite ends of the cell by the spindle fibers
• Takes about 10 minutes
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
MitosisTelophase
• Nuclear membrane forms around each group of chromosomes
• Chromosomes unwind and become long and thin again
• Cytokinesis begins
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
MitosisCytokinesis
• Cytoplasm divides • One cell becomes two individual cells• Different in plants and animals
– Animals:• Cell membrane pinches in
– Plants:• Cell wall forms down the center
http://www.dundee.ac.uk
http://www.biologycorner.com/bio1/cellcycle.html
http://www.iknow.net/CDROMs/cell_cdrom/cell3.html
Animation
http://www.johnkyrk.com/mitosis.html
Animation
http://www.cellsalive.com/mitosis.htm