Download Chapter 10 Section 2 Notes

THE PROCESS OF
CELL DIVISION
Chapter 10 Section 2
CHROMOSOMES
Cells carry LOTS of DNA
DNA in E.Coli is ~ 1000X the length of the cell.
Has to be packaged tight and safely
Chromosomes
Help for Cell Division
KEY QUESTION
What is the job of
chromosomes in cell
division?
Chromosomes make
it possible to separate
DNA precisely in the
cell.
THE CELL CYCLE
Cells divide all the time to
make new cells. The series
of cells growth and
division is the cell cycle.
Cell Grows
Prepares for Division
Divides
get 2 Daughter cells
PROKARYOTIC CELL CYCLE
Steps
Fast
Binary Fission (asexual
reproduction)
Growth, DNA
replication, Cell
Division
EUKARYOTIC CELL CYCLE
2 Parts: Interphase and
Mitosis
Steps of Interphase
G1: Cell Growth
S Phase: DNA Replication
G2: Preparing for Cell
Division
Mitosis: Cell Division
KEY QUESTION
What are the main events in the cell cycle?
During the cell cycle, a cell grows, prepares for
division, and divides to form 2 daughter cells.
The eukaryotic cell cycle has two parts:
Interphase and Cell Division
MITOSIS
The nucleus is dividing continuously, but we have identified
4 phases:
Prophase
Metaphase
Anaphase
Telophase
PROPHASE
Chromatin coils up into chromosomes (packaged DNA)
Chromosomes look like an X, the two separate V’s are called
sister chromatids
The centromere holds them together. The centromere also
helps the chromosome with movement.
Nucleolus disappears and the nuclear envelope disintegrates
In animal cells, we use centrioles, they move to opposite ends
of the cells and begin to release spindle fibers.
METAPHASE
Spindle fibers attach to the
chromosome by the centromere, and
the spindle fibers line them up in the
middle of cell.
There is a spindle fiber pulling the
sister chromatid to each end of the
cell.
This way when they divide each new
cell has an identical copy of the
DNA.
ANAPHASE
Chromosomes split and
the chromatid pairs
are pulled to each end
of the cell.
The microtubules
just shorted and pull the
chromatids back toward
the centrioles.
Chromatids reach the opposite ends of the
poles.
New cells start to prepare
Chromosomes unwind, to make proteins
Spindle fibers break down
Nucleolus reappears
Nuclear envelope reforms until we get two
nuclear double membranes around the new
sets of chromosomes
CYTOKINESIS
Different for plants and animals.
Why?
Animals: plasma membrane pinches in along equator in
telophase, keeps pinching until they form 2 new cells.
Plants: Cell wall so it can’t pinch in, but a cell plate is
formed on each side until the separation of the cells is
complete.
ANIMAL VS PLANT
WHY DO WE NEED MITOSIS?
We get 2 new cells that are identical to the parent cell.
Carry out the same function as the parent cell.
Unicellular vs. Multicellular
Unicellular: asexual reproduction (usually binary
fission for most unicellular organisms)
Multicellular: making copies, or new cells
STAGES OF MITOSIS
ONION ROOT MITOSIS