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