Download Cell Division Mitosis

The Cell Cycle:
Mitosis &
Asexual
Reproduction
Why do cells divide?
• Growth
• Development
• Repair
Essential Features of Cell Division
1.
Transmit a complete copy of
Genetic information (DNA).
2.
Transmit materials necessary for
cell to survive and use genetic
information.
Cell Cycle
Activities of a cell from one cell
division to the next
– Cell grows
– DNA is replicated
– Cell divides into two identical daughter cells
Two Fundamental Types of Cells
• Prokaryotic
• Eukaryotic
Prokaryotic Cell Cycle
• Prokaryotic chromosome a circular loop
• Prokaryotes multiply by binary fission
1. chromosome attaches to plasma
membrane
2.
chromosome is replicated
3. cell elongates – new plasma membrane
and cell wall are added between
chromosomes, pushing them towards
opposite ends of cell
4. parent cell is divided into two identical
daughter cells
What is Mitotic Cell Division?
Division of Somatic (body) cells
(non reproductive cells)
in eukaryotic organisms.
- A single cell divides into two identical
daughter cells
- Daughter cells have same # of
chromosomes as does parent cell.
Packing for the move…
When cell is not dividing…
•DNA molecules in extended, uncondensed
form = chromatin
•Cell can only use DNA for Replication and
Protein Synthesis when in extended
state.
When cell is preparing for division…
DNA molecules condense to form
chromosomes prior to division.
• each chromosome is a single molecule
of DNA
• easier to sort and organize DNA into
daughter cells
http://www.ictscience.co.uk/page08.asp
Structure of a eukaryotic chromosome
• Unreplicated chromosome
arm
arm
centromere
Prior to cell division:
• chromosomes (DNA) are replicated
• replicated chromosome
– attached at their centromeres
– as long as attached, known as
sister chromatids
replicated
chromosome
sister
chromatids
daughter
chromosomes
Karyotype
• The complete set of
chromosomes of a cell of
any living organism.
• The chromosomes are
arranged and displayed
(often on a photo) in pairs,
ordered by size.
• Using the karyotype, can
you identify the sex of the
person?
– male
arm
arm
centromere
Karyotype
Ploidy – refers to the number of sets of
homologous chromosomes in a cell
● Haploid– one copy of each chromosome
– designated as “n”
● Diploid– two copies (= pair) of each chromosome
– designated as “2n”
Diploid organisms receive one of each type of
chromosome from female parent (maternal
chromosomes) and one of each type of
chromosome from male parent (paternal
chromosomes)
A “matched” pair of maternal and paternal chromosomes
are called homologues
http://www.britannica.com/eb/subject?idxStructId=116055
Haploid, Diplod, Homologous,
Replicated, Chromatids,
Chromosomes…
AAArrrrgggghh!
Replicated Chromosomes
Sister Chromatids
Unreplicated
Replicated
Homologous Chromosomes
Homologous vs.
Replicated
Eukaryotic Cell Cycle
2 major phases:
• Interphase (3 stages)
– DNA uncondensed
(= chromatin)
• Cell Division (4 stages + cytokinesis)
- Nuclear division & division of cytoplasm
– DNA condensed (= chromosomes)
Interphase
non-dividing state
3 sub-stages:
G1 – cell grows in size
– organelles replicated
S
– replication of DNA
– synthesis of proteins associated
with DNA
G2 – synthesis of proteins associated
with mitosis
Mitotic Cell Division
2 major processes:
• Mitosis – nuclear division
=> preserves diploid number of
chromosomes
• Cytokinesis – cytoplasmic division
=> cell divides into two daughter cells
Mitosis
4 sub-phases:
1st – Prophase
2nd – Metaphase
3rd – Anaphase
4th – Telophase and Cytokinesis
Secret to remembering phases in order…
I Play Mariokart At The Courthouse
DEMOs: http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
http://www.cellsalive.com/mitosis.htm
Prophase
• 3 major events
i) chromosomes condense
ii) spindle fibers form
iii) chromosomes are captured by
spindle
Mitotic Spindle
Forms
• spindle fibers are specialized
microtubules
• spindle fibers radiate out from
centrioles, forming the “aster”
• centrioles occur in pairs, and are
duplicated during interphase
chromatin
nucleus
condensing
chromosomes
nucleolus
centrioles
kinetocore
Prophase
Metaphase
• chromosomes align along
equator of the cell, with one
kinetochore facing each pole
centrioles
chromosomes
spindle fibers
Anaphase
• sister chromatids separate
• spindle fibers attached to
kinetochores shorten and pull
chromatids towards the poles.
• free spindle fibers lengthen and push
poles of cell apart
Telophase
• spindle fibers disintegrate
• nuclear envelopes form around both
groups of chromosomes
• chromosomes revert to their extended
state
• nucleoli reappear
• cytokinesis occurs, enclosing each
daughter nucleus into a separate cell
Early Telophase
chromosomes
decondensing
pinching of cell
membrane at equator
nuclear envelope
reforming
nucleolus reappears
cytokinesis
Late Telophase
Cytokinesis – Plant vs. Animal Cells
• Plant cells undergo
cytokinesis by forming a
cell plate between the
two daughter nuclei
• Animal cells undergo
cytokinesis through the
formation of a cleavage
furrow. A ring of
microtubules contract,
pinching the cell in half.
Lets
plaaaay…
“Guess
That
Phase!”
DEMOs: http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
http://www.cellsalive.com/mitosis.htm
Phases and Sub-phases of Cell Division
a. G1
1. Interphase
b. S
c. G2
1. Prophase
2. Metaphase
a. Nuclear division
3. Anaphase
2. Mitosis
4. Telophase
b. Cytokinesis
Mitosis Demo Then Practice
• Break up into groups.
• Use chromosome kits to work through the
stages of mitosis.
• You are not required to have me approve your
demo, but I advice that you do have me come
over to your group and make sure that you have
it right.
• Mitosis worksheet due at end of class.