8-2 Cell Division
(Part I)
Mitosis and Cytokinesis
Eukaryotic Cell Division
 2 Main Stages
 Stage 1: Mitosis—division of the
cell nucleus, resulting in 2 nuclei
identical to the first
 Stage 2: Cytokinesis—division of
the cytoplasm into 2 distinct cells
(daughter cells)
Chromosomes
 Structures in the nucleus that
contain genetic information that is
passed to future generations
 Name means “colored body”
 Made of DNAchromatin
 Circles in prokaryotes
 Strands in eukaryotes
 Each species has a certain number
Chromosomes (cont.)
 Not normally visible
 Only during cell division
 Prepare for mitosis:
 DNA is copied (why?)
 DNA supercoils into condensed
chromosome structure
 2 copies hooked together by a
centromere
 Each copy = a chromatid
8-2 Cell Division
(Part 2)
Mitosis and Cytokinesis
The Cell Cycle
 The time from the beginning
of one mitosis to the
beginning of the next
 It is a CYCLE, this means…
 As soon as it’s done, it starts
over again
 Time frame is different for each
type of cell
 Most muscle and nerve cells—
never
 Lining of digestive tract—every 6
hours
Interphase
 The period between cell
divisions
 Normal cell function
 Three stages
 G1—longest stage
 S—DNA replication
 G2—gearing up for mitosis
Prophase
 Longest phase
 Chromosomes appear
(condensed)
 Centrioles move to opposite
poles
 Spindle forms
 Nuclear envelope breaks down
Metaphase
 Shortest phase of mitosis
 Chromosomes line up along
equator of the cell
 Spindle connects to
centromeres
Anaphase
 Centromeres split
 Sister chromatids separate
 Spindle pulls chromosomes
to opposite poles
Telophase
 Final phase of mitosis
 Chromosomes begin to uncoil
 Nuclear envelope reforms
 Spindle breaks apart
 Mitosis is complete
Cytokinesis
 Quickly follows mitosis
 Organelles are divided between
2 new cells
 Animals: cell membrane pinches
in
 Plants: cell plate forms