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But what actually happens when a cell divides?
http://video.google.com/videoplay?docid=-5522357274832025243&q=mitosis&total=368&start=0&num=10&so=0&type=search&plindex=2
http://www.johnkyrk.com/mitosis.html http://www.bio.unc.edu/faculty/salmon/lab/mit
osis/mitosismovies.html
Interphase: In between cell divisions
The working cell It grows in size (protein synthesis) It copies it’s genetic material (replication)
Nucleus
Nucleus envelope
Centriole
Nucleolus
Cytoplasm
Plasma membrane
© 2010 Paul Billiet ODWS
Prophase: Division begins
Centriole divides
Treads appear in the nucleus =
Chromosomes condensing
Nucleus swells
Nucleolus disappears
© 2010 Paul Billiet ODWS
End of prophase: The nucleus disappears
Nucleus envelope breaks down
Spindle fibres grow out from the ends of the cell
CentromereSister chromatids
Chromosomes appear as two threads (the chromatids) joined by a constriction (the centromere)
© 2010 Paul Billiet ODWS
Metaphase: The chromosomes are organised
Chromosomes line up across the equator of the spindle
Joined to fibres by their centromeres
© 2010 Paul Billiet ODWS
Anaphase: The chromosomes split
The sister chromatids of each chromosome split
The spindle pulls one to each pole
© 2010 Paul Billiet ODWS
Telophase: The end of mitosis The nuclei reform Each one contains a complete set
of chromosomes A new nuclear envelop forms The chromosomes uncoil
The cytoplasm divides in two to form two identical daughter cells
The cells goes back to work
© 2010 Paul Billiet ODWS
Chromosomes and cell division
Multicellular organisms copy their chromosomes before cell division
They must grow to a mature size
The nucleus divides, distributing the chromosomes into two equal groups
Interphase
The cytoplasm then divides each part taking a nucleus
Mitosis
Cytokinesis
© 2010 Paul Billiet ODWS
The cell cycle
G1 + S + G2 = INTERPHASE
First growth phase.Varies in length
Copying of chromosomes
Some cells may stay in this stage for over a year
Second growth period
M
G1
S
G2
G0
Cytokinesis division of the cytoplasm
© 2010 Paul Billiet ODWS