Transcript Cell Division

THE CELL CYCLE
and
CELL DIVISION
Think about it…
why do cells stay small?
DNA Overload = Limit to Cell Growth
The information stored in that DNA is able to
meet all of the cell’s needs in a small cell
If a cell grows too large, the DNA cannot
produce enough proteins to supply the cell
CELL DIVISION
-before it becomes too large, a growing
‘parent’ cell divides into 2 ‘daughter’ cells
**Before cell division occurs, the cell
replicates all of its DNA, one set/daughter
**2 main stages of eukaryotic cell division:
1. Mitosis – division of the cell nucleus
2. Cytokinesis – division of cell cytoplasm
Liver cell completes cell division – Magnification 11,500x
Chromosomes
 Genetic information is passed from one
generation to the next on chromosomes (made
of DNA).
 Chromosomes are only visible in most cells
during cell division (other times, the DNA is in
the not visible chromatin state)
 Before cell division, the DNA condenses into
compact structures, chromosomes
Chromosomes
 Once copied, each
chromosome consists of
two identical “sister”
chromatids.
Sister chromatids
 Centromere –attachment
 After cell division, each
new cell receives one
sister chromatid
Centromere
THE CELL CYCLE
The Cell Cycle
 During the cell cycle:
 a cell grows
 prepares for division
 divides
 Interphase is the period of growth that occurs
between cell divisions
-followed by mitosis and cytokinesis
The Cell Cycle
increases in size
synthesizes proteins & organelles
chromosome
replicated
DNA synthesis
takes place
Enters S phase
completes cycle
organelles and molecules required for cell division are produced
Once G2 is complete, the cell is ready to start the M phase—Mitosis
Mitosis
The process of cell division which results
in the production of two daughter cells
from a single parent cell
The daughter cells are identical to
one another and to the original parent
cell.
Animated Cycle
http://www.cellsalive.com/cell_cycle.htm
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_the_
cell_cycle_works.html
Mitosis




Prophase
Metaphase
Anaphase
Telophase
Mitosis: PROPHASE
Spindle
forming
Prophase
Chromosomes
(paired
chromatids)
Centromere
Prophase
Spindle
forming
 1st & longest phase
 Centrioles separate and
take up positions @
nuclear poles
 Spindle, a microtubule
structure, forms between
the centrioles
 Nuclear envelope breaks
down.
Centromere
Chromosomes
(paired
chromatids)
Mitosis: METAPHASE
Centriole
Spindle
Centriole
Metaphase
Centriole
Metaphase
The chromosomes
line up across the
center of the cell aka
metaphase plate
Microtubules connect
the centromeres to
the fibers of the
spindle.
Spindle
Mitosis: ANAPHASE
Individual
chromosomes
Anaphase
 Anaphase
Sister chromatids
separate into
individual
chromosomes.
The chromosomes
move and separate
into two groups.
Individual
chromosomes
Mitosis: TELOPHASE
Nuclear
envelope
reforming
Telophase
Telophase
Chromosomes gather
at opposite ends of the
cell & lose their distinct
shape
New nuclear envelopes
forms around each
cluster
Spindle breaks apart &
nucleoli reappear
CYTOKINESIS
Cytokinesis
Cytokinesis
 Not a phase of mitosis
 Cell membrane pinches
in and the cytoplasm is
split between the 2 cells
 Each daughter cell has
an identical set of
duplicate chromosomes
Cytokinesis in Plants
 Cell plate
forms midway between the divided nuclei.
Cell plate
Cell wall
Animal Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Plant Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Cells in Mitosis
http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html
http://web.mac.com/mrgaskell/iWeb/Science%20Extras/Mitosis%20Slides.html
Things to look:
Shape of Cell & If there is a division forming between cells
Chromosomes & Location
Presence of a nucleus
Mitosis Animations
 http://www.johnkyrk.com/mitosis.html
 http://www.youtube.com/watch?v=VlN7K19QB0
 http://outreach.mcb.harvard.edu/animations/bio
chem.swf
 http://www.hybridmedicalanimation.com/anim_
mitosis.html
 http://www.biology.arizona.edu/Cell_bio/tutorial
s/cell_cycle/cells3.html
Controls on Cell Division
 Normal cells reproduce until they come
into contact with other cells.
 When cells come into contact with other
cells, they respond by not growing.
 This shows that cell growth and division
can be turned on and off.
Cell Cycle Regulators
 Regulated by a specific protein called cyclin
 Cyclin concentration rises and falls in time
with the cell cycle
o Internal Regulators:
-Proteins responding to events inside cell
- Allow the cell cycle to proceed only when
certain processes have happened inside the cell.
o External Regulators:
-Proteins responding to events outside cell
-direct cells to speed up/slow down the cell
cycle
Cancer:
Uncontrolled Cell Growth
 cells lose the ability to control growth.
 Cancer cells do not respond to the signals that
regulate the growth of most cells.
 Cancer cells divide uncontrollably and form
masses of cells called tumors that can
damage the surrounding tissues.
 Metastasis-cancer cells may break loose from
tumors and spread throughout the body
Cancer Cells
 http://science.education.nih.gov/suppleme
nts/nih1/cancer/activities/activity2_animati
ons.htm
Interphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Meiosis
 cell division by which germ cells (eggs and
sperm) are produced.
One parent cell produces four daughter
cells (not genetically identical)
During meiosis, DNA replicates
once, but the nucleus divides twice.
Daughter cells have half the number
of chromosomes (n=haploid) found in
the original parent cell (2n=diploid)
Meiosis I
• Prophase 1: Each chromosome duplicates and
remains closely associated. These are called sister
chromatids.
• Metaphase 1: Chromosomes align at the center of the
cell.
• Anaphase 1: Chromosome pairs separate with sister
chromatids remaining together.
• Telophase 1: Two daughter cells are formed with
each daughter containing only one chromosome of the
chromosome pair.
Prophase I
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Prophase I
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Metaphase I
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Telophase I
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
MEIOSIS II
• Prophase 2: DNA does not replicate.
• Metaphase 2: Chromosomes line up at the center of
the cell
• Anaphase 2: Centromeres divide and sister
chromatids move separately to each pole
• Telophase 2: Cell division is complete
4 haploid daughter cells are formed
Prophase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Metaphase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Telophase II
http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html
Meiosis
http://www.biosci.uga.edu/almanac/bio_103/notes/apr_3.html.
Meiosis Animation
http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/movie/meiosis.htm
Crossing Over
A section of 1 chromosome switches places with
the same section from the other chromosome
http://www.accessexcellence.org
http://post.queensu.ca/
Differences in Mitosis & Meiosis
• Mitosis
–
–
–
–
Asexual
Cell divides once
Two daughter cells
Genetic information is
identical
• Meiosis
– Sexual
– Cell divides twice
– Four haploid daughter
cells
– Genetic information is
different
Purpose of Reproduction
• To make sure a species can continue.
– Definition: Reproduction is the process by
which an organism produces others of its
same kind.
Asexual Reproduction
• A new organism produced from 1 organism
• The offspring will have hereditary material
uniform with the hereditary material of the
parent organism. This means they will be
genetically alike.
Sexual Reproduction
• Requires two sex cells – egg and sperm
• The egg and sperm join to form an entirely
new organism
– Different from the parent organism
IMPORTANT!
• Asexual reproduction results in offspring
that are genetically identical to the parent
organism
• Sexual reproduction results in offspring
that are genetically different from the
parent organisms-more energy so….
WHY IS IT WORTH IT?
Comparison Animations
http://www.pbs.org/wgbh/nova/baby/divi_flash.html
http://www.usoe.k12.ut.us/curr/science/sciber00/7th/gen
etics/sciber/animatin.htm