Mitosis
• Definition: nuclear division and cytokinesis
• Functions:
• tissue growth and repair
• asexual reproduction (binary & multiple fission)
Cell division requires coordinated division of
chromosomes (mitosis)…
…and division of the
cytoplasm (cytokinesis).
Because DNA stores genetic
information and is faithfully
replicated, information is passed
largely unaltered from cell-to-cell,
generation-to-generation.
Proteins and
Their Production
The Primary
Reason for DNA
DNA is Packaged into Chromosomes
duplicated
chromosome
chromatin
Two meters DNA fit into a sphere ~ 0.000005
meters in diameter.
The Link Between DNA Replication and Chromosome Duplication
Anatomy of a Chromosome
DNA is Condensed into Visible Chromosomes Only
For Brief Periods in the Life of a Cell
95% of the time,
chromosomes are like this.
A Karyotype is an Arranged Picture of
Chromosomes At Their Most Condensed State
Note that almost all chromosomes come in homologous pairs.
Boy or
girl?
A normal
human
karyotype
Prophase
• nuclear membrane
disintegrates
• chromatin thickens
• spindle apparatus
appears
Metaphase
• chromosomes line up
on the equatorial plane
Anaphase
• centromers divide
• chromatids move
toward opposite poles
Telophase
• nuclear membrane
reforms
• cytokinesis
• daughter cells
Cytokinesis
In Animal Cells, a
Cleavage Furrow
Forms and Separates
Daughter Cells
Cleave furrow in a dividing frog cell.
In plants, a cell plate forms; separating
daughter cells during cytokinesis
Stages of Mitosis
• Prophase– DNA is condensed and packaged
• Metaphase– “middle stage”; Condensed
chromosomes line up along the equatorial plane.
• Anaphase- Copies of each chromosome move to
opposite poles of the cell.
• Telophase– “end stage”; Nuclear membranes
reform around the chromosomes and cytokinesis
occurs resulting in two daughter cells.
Cancer is Runaway Mitosis
Licentious division - prostate cancer cells during division.