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The Cell Cycle: Mitosis Notes
Facts
* Somatic cells – “soma” means
body
* Body cells each contain the
same number of chromosomes
*How many chromosomes do
human body cells have?
Chromosome = cell structure
that contains the genetic
material in the form of DNA.
This is located inside the
nucleus.
Centromere = cell structure
that joins two chromatids
together to form a sister
chromatid.
Chromatid = one copy of the
original chromosome.
Sister chromatid = identical
halves of the duplicated parent
(original) chromosome formed
during interphase.
Interphase
The time between the formation
of the cell and the next mitosis
The longest part of the cell cycle
Divided into three parts
G1 phase (1st Growth Phase)
~cell grows rapidly
~cell carries out normal functions
~organelles duplicate
~this phase occupies most of the
cell’s life
S Phase (Synthesis)
~DNA is replicated (copied)
~At the end, each individual
chromosome consists of two
chromatids attached at the
centromere.
G2 Phase (2nd Growth phase)
~ cell is getting ready to divide
~ organelles are duplicating
~ microtubules are assembled to
move the chromosomes during
mitosis
Phases of Mitosis
Prophase – this is the first step
of mitosis and it lasts the longest.
Usually 60% of the total time for
mitosis.
~ Chromosomes coil up into short
rods
~ Nucleolus and nuclear membrane
disappear
~ Spindle fibers form between
centrioles
~ Centrioles move to opposite
ends of the cell
Metaphase – second phase of
mitosis
~ Meta = middle
~ Centromeres of
chromosomes attach to
spindle fibers
~ Chromosomes align along the
middle of the cell (equator)
Anaphase – third phase of
mitosis
~ Centromeres separate
~ Chromatids separate and
become separate chromosomes
again
~Spindle fibers pull
chromosomes apart to opposite
ends of the cell
~Cell membrane begins to pinch
in the middle
Telophase – final stage of mitosis
~ Nuclear membrane forms around
each set of chromosomes
~ Nucleolus reappears
~ Chromosomes return to
threadlike form
Cytokinesis – the division of
the cytoplasm
Animal cells – cell membrane
pinches in at the end of
telophase and two new
identical daughter
cells are produced.
Plant cells – since plant cells
have a rigid cell wall, the cell
membrane can’t just pinch in.
So, a cell plate forms across the
middle of the cell to divide the
two cells into two separate cells.