Download Mitosis

Mitosis
Why Mitosis?
 The purpose of mitosis is to
generate two new cells from one
cell.
 The “daughter cells” generated are
exact copies of the “parent cell”
 Mitosis is happening in many cells
in your body as we speak!
 Some cells divide more frequently
than others
Mitosis is part of the
Cell Cycle
Mitosis
Cytokinesis
Interphase
Key Events in the Cell Cycle
 The cell gets larger
Interphase
 Organelles are made
 Genetic information is duplicated
 Half of the DNA and organelles go to
one end and the other half to the
opposite end
 The cell is split down the middle to
make 2 new cells
Interphase
G2
Mitosis
Cytokinesis
 Gap1 (G1)
 Preparation for growth
 Organelles, membranes, and
ribosomes made
 Synthesis (S)
 Chromosomes replicated
 Gap2 (G2)
 Preparation for division
 Mitochondria divide
Q4 Part 1
 Remember, mitochondria have their
own chromosome!
S
G1
Key Events in the Cell
Cycle
 The cell gets larger
Interphase
 Organelles are made
 Genetic information is duplicated
Mitosis
 Half of the DNA and organelles go
to one end and the other half to the
opposite end
 The cell is split down the middle to
make 2 new cells
Q7
Chromosomes in Somatic
Cells
Nucleus of cell during G1
Chromosomes not duplicated
Homologous pair
Nucleus of cell after S phase
Chromosomes are duplicated
Nucleus of cell after mitosis
Chromosomes are not duplicated
Keep in Mind…
Mitosis




Prophase
Metaphase
Anaphase
Telophase
P
M
A
T
Cytokinesis
Interphase
Prophase
 Pro =forward, forth
 Chromosomes condense
 Nuclear envelope breaks down
 Membrane surrounding the nucleus
 Centrioles move to opposite poles
 Spindle fibers grow
Q4 Part 2
Metaphase
 Meta =after, with
 Chromosomes line up at the midline
 Spindle attaches to chromosomes at the
centromere
 The centromere is where the sister
chromatids are attached
Q4 Part 2
Anaphase
 Ana =against
 Centromeres split
 Sister chromatids are pulled to opposite
poles by the shortening of spindle fibers
 Once separated, each sister chromatid is
now a chromosome (and each is exactly like
the chromosome found in the original cell
before S of interphase)
Q4 Part 2
Telophase
 Telo =completion of a goal
 Spindle breaks down
 Nuclear envelope forms in each
of the daughter cells
 Chromosomes decondense
Q4 Part 2
Key Events in the Cell
Cycle
 The cell gets larger
Interphase
 Organelles are made
 Genetic information is duplicated
Mitosis
Cytokinesis
 Half of the DNA and organelles go
to one end and the other half to the
opposite end
 The cell is split down the middle to
make 2 new cells
Q7
Cytokinesis
Mitosis
Cytokinesis
 “Cell-making” phase
 Organelles and
cytoplasm are
distributed between
daughter cells
 Microfilament band
at equator contracts
to pinch apart 2 new
daughter cells
Interphase
Summary of Cell Cycle
G1
S
G2
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis






Cell grows
DNA replicates
Organelles are made
Chromosomes condense
Chromosomes line up at the equator
Replicated chromosomes are pulled
apart to opposite poles
 Chromosomes decondense
 Two daughter cells are formed
I Pee on
the
MAT,
See?
P
M
A
T
I
C
Go
G2
Mitosis
Cytokinesis
 Resting phase
 Cell may:
S
 Enter S phase
 Die
 Cell is damaged
 Do nothing
 Neuron
G1
Go
Cell Death
Sit tight
Cell Cycle Checkpoints
G2
Mitosis
Cytokinesis
S
DNA damage checkpoints
Spindle checkpoint
G1
Apoptosis
 Programmed cell death
 Neat and orderly
Necrosis
 Cell explodes
 Not so neat and orderly
 In response to injury
Telomeres
 Consist of a repeated sequence
of DNA
 Nature’s solution to the end-replication problem
 Very tips of chromosomes cannot be replicated




Shortened with each mitotic division
Limits # of possible cell divisions
Cell will not divide after ~50 divisions
Not found in eggs/sperm, bone marrow cells, cancer
cells
 Shortening is hastened by chronic stress
Cell Differentiation
 The process whereby a cell becomes specialized
 Every cell contains the exact same genetic
information (all 23 chromosome pairs)
 One chromosome from mom and one from dad
 Not all genetic info is being used by every cell
 Different cell types are making
different proteins
 The proteins being made by a cell
give it specialized characteristics
(e.g. blood cell vs. brain cell)
Stem Cells
 Important for regenerating cells that are lost (e.g. skin
cells) and for growth
 Stem cells are undifferentiated
 Totipotent =able give rise to any cell type
 Progenitor cells
 Somewhat specialized
 Pluripotent =able to produce many
different cell types
Pathways to Cell
Specialization
 Each specialized
cell type uses
only certain
“recipes” from
the “cookbook”
Embryonic Stem Cells -IVF
 Yields totipotent cells
 Uses frozen embryos from in vitro
fertilization
 in vitro =in a dish
 in vivo =in the body
Embryonic Stem Cells –
Nuclear Transfection
Cloning
Adult Stem Cells
 Pluripotent
 Found in bone marrow,
umbilical cord blood,
certain parts of the brain
Even I
have stem
cells!