Download Cell Cycle and Mitosis

The Cell Cycle
&
Cell Division
Cells have a life cycle
• Cells develop and grow
• Somatic cells (body cells) of a multicellular
organism perform specialized functions to
keep the organism functioning
• Life cycle of a cell is called the Cell Cycle
– Interphase
– Mitosis
The Cell
Cycle
The Cell Cycle
• The sequence of growth and division
of a cell.
• ~95% of cell cycle in interphase
• Time when cell carries out its
function
• ~5% of cell cycle in mitosis
• Cell divides
Interphase
The cell prepares for division
• Cell carries out its “life”
functions
– Maintains homeostasis and
carries out metabolic
reactions
• DNA replicated
• Organelles replicated
• Cell increases in size
Chromosomes
• Homologous Chromosomes
– Pair of chromosomes that have the same types of
genes on them in the same locations
• Sister chromatids
– A duplicated chromosome
– Created after DNA replication
• Centromere
– Holds sister chromatids together after DNA
replication
Chromosomes
Before replication = 2 copies of each chromosome (homologous pair)
After replication = 4 copies of each chromosome (sister chromatids
within a homologous pair)
Cell Division: Mitosis
• Cells leave interphase and enter mitosis to…
– Maintain size
– Growth and repair
– Asexual reproduce (unicellular organisms)
Mitosis can be divided into stages
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis
Prophase
The cell prepares for nuclear division
• DNA condenses into
chromosomes
• Nuclear membrane
disappears
Metaphase
Chromosomes line up on the metaphase
plate
• Chromosomes line up at
the center of the cell
• Spindle fibers attach to
the chromosomes at
the centromere
Anaphase
The chromosomes divide and separate
• Spindle fibers pull
chromosomes apart by
separating the sister
chromatids of each
homologous pair
Telophase
The Nuclei Return
• Chromosomes begin to
uncoil
• Nuclear membranes
begin to form
Cytokinesis
The cytoplasm divides
• Cytoplasm divides and
separates
• Cleavage furrow
pinches cell membrane
between the two new
nuclei
• Happens at the same
time as telophase
• 2 identical daughter
cells are formed