Transcript Mitosis & Cytokinesis Notes

The Cell Cycle
Mitosis & Cytokinesis
Why do living things grow?
• This baby
king penguin
grows
because he
produces
more and
more cells.
How do cells know when to
quit dividing?
• Cell growth and cell division are
CAREFULLY controlled.
• Only certain cells are allowed to
divide rapidly.
–Ex. Hair follicles & stomach lining.
Experiment on Cell Growth
•One experiment using
cells in a petri dish
showed that they
stopped dividing when
they touched!
•But……
That’s not always the case…
Breast cancer cell
Liver Cancer cells
SCARS-why do they look different?
• Scar Tissue is not of the same
quality as unscarred skin.
• It is less capable of resisting
ultraviolet radiation.
• It will not regrow hair follicles.
• It will not regrow sweat glands.
Mitosis
• The process where the
nucleus is divided into two
new, IDENTICAL, nuclei.
During the early stages of
Mitosis…
•The chromatin (DNA +
Proteins) becomes
condensed and you
can see the
chromosomes.
Supercoiling cont.
Histones- Special proteins
the DNA coils around.
Nucleosomes- A coiled,
beadlike structure of DNA
wrapped around a histone.
Chromosomes
• Chromosomes contain highly
supercoiled strands of DNA.
p. 225 in
your book
shows
supercoiling
A Chromosome
*Two sister CHROMATIDS
Make up the chromosome
*The CENTROMERE, a sticky
Spot in the middle of the
Chromosome, keeps the sister
Chromatids together.
The Cell CycleI,P,M,A,T & Cytokinesis
•Read pages228-229
•Write down what
parts make up the cell
cycle.
Interphase p. 228
• A long period between cell divisions.
• 3 phases G1, S, G2
–G1, Cell grows
–S, DNA doubles
–G2, Organelles double