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
Mitosis
The Cell Cycle
• The nucleus divides in several phases:
– Interphase
– Prophase
– Metaphase
– Anaphase
– Telophase
Mitosis
Interphase
• 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
Mitosis
Prophase
• 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
Mitosis
Metaphase
• 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
Mitosis
Anaphase
• 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
Mitosis
Telophase
• 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
Mitosis
Cytokinesis
• 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