Download Chapter 10 Cell Division

CHAPTER 10: Cell Division
Why Cell Division?
• (We will use the following analogy to
understand cell division.)
ANALOGY
• A cell is like a town.
• The DNA in the nucleus is like the books in
a library.
• The nucleus doesn’t grow and the DNA
doesn’t increase in a cell.
Town Library Analogy
• SITUTION: You have a research
project. Your town has grown
from 1000 to 10, 000 people, but
the library is unchanged.
• QUESTION: What is going to
happen when you go to check out
books for your project?
Town Library Analogy
• ANSWER: Books won’t be
available. The staff may be
having a hard time restocking
books, even if they have been
returned.
Town Library Analogy
• SOLUTION: Build
another library in another
section of town, stock it
with additional copies of
books.
CELL
• The cell has the same 2 problems.
• DNA Overload: The DNA gets to
a point where it can’t do more
things at the same time.
• Exchange of Materials: After a
certain size, the cell can’t
efficiently transport nutrients (in)
and wastes (out)
CELL
• SOLUTION: The cell will
make an exact copy of itself
and divide.
• 2 small cells with identical
information and able to
transport materials easily.
DNA Replication
•DNA stores genetic
information
•It gets replicated
(copied) before the cell
divides
•Therefore, each
generation of cells is
identical
CELL
CYCLE:
The
process a
cell
repeats
every
time it
divides
INTERPHASE: When the Cell is
NOT Dividing
• G1: & G2 phases: growth
• S Phase: “synthesis”when the DNA is
replicated
2 Important
Parts of Cell
Division
1. Mitosisdivision of the
nucleus
2. CytokinesisDivision of the
cytoplasm
(cell splits)
MITOSIS ↓
CYTOKINESIS
↓
STAGE 1 OF MITOSIS: PROPHASE
•DNA is Packaged into Chromosomes
•Centrioles move to opposite sides of
cell as spindle begins to form
•Nuclear envelope breaks down
duplicated
chromosome
chromatin
prophase
STAGE 2 OF MITOSIS: METAPHASE
•Chromosomes line up in center of cell
•Each chromatid is attached to a spindle
fiber at its centromere
metaphase
STAGE 3 OF MITOSIS: ANAPHASE
•Sister chromatids separate &
move to opposite ends of cell.
STAGE 4 OF MITOSIS: TELOPHASE
•Chromosomes are at opposite ends of
cell & become chromatin again
•New nuclear envelopes form
Mitosis in Action
Blue
shows
DNA,
green
shows
spindle
fibers.
AFTER MITOSIS: CYTOKINESIS
cell divides into 2 cells
ANIMAL CELL:
Pinches into 2 cells
PLANT CELL: cell walls
forms between 2 new cells
REGULATION OF CELL CYCLE
Cyclins are chemicals that control
cell division
1. Internal Regulators-cyclins
inside the cell that control its
division
2. External regulators- cyclins
outside the cell that control its
division
Example of Regulators
• Internal: When you get a cut,
your cells send out cyclins so
that new cells will be made (cell
division)
• External: When the cells touch
(cut is healed), cyclins tell cells
to stop dividing.
Cancer Is One Outcome of A Runaway Cell Cycle
Licentious division - prostate cancer cells during division.
CANCER: Regulators out of Control
• Cancer: cells dividing out
of control
• Often an error in the p 53
gene that regulates cell
division
Why Cancer is a Problem
–Cancer cells aren’t poisonous
–They rob your body of nutrients.
–They can develop their own
network of blood vessels.
•Rob your body faster
•Pathway for cancer to spread
through your body. (“metastasis”)
Cancer Treatment
Chemotherapy & Radiation
are used to kill cancer cells.
1.Benefits: cancer cells are
killed
2.Drawbacks: many healthy
cells can be killed too.
Chemotherapy
•Use of medications
Radiation
•Use of exposure to
radioactive
elements, which
destroy cells.