Transcript Chapter 9 PowerPoint Lecture

• Cell Division and
Mitosis
•
-Chapter 9-
• Honors Biology Program
• Mountain Pointe High School
Development Of A Human Hand
future arm and hand of embryo,
five weeks old
Overview: Key Roles of Cell Division
• Reproduction
distinguishes living from non-
living
• Multicellular organisms develop from a
zygote.
• Cell division aids in repair & renewing of
cells
Overview: Key Roles of Cell Division
• Cell
division results in genetically identical
daughter cells.
• Exact copy in each daughter cell.
• A cells genetic information, package in
DNA, is called its genome.
• In prokaryotes DNA a long single
strand
• Eukaryotes several DNA molecules.
Overview: Key Roles of Cell Division
• In
meiosis gametes are
produced (egg & sperm
cells).
• Meiosis yields 4 nonidentical daughter cells
with ½ the number of
chromosomes.
The Cell Cycle
Eukaryotic cells
divide in a
series of steps
known as the
Cell Cycle.
Three main parts:
(a) Interphase
(b) Mitosis
(c) Cytokinesis
End result: two
genetically
identical
“daughter
cells”.
Interphase
• It’s important to
understand that
during Interphase,
no division is taking
place!
• Interphase is
divided into three
stages:
• G1
• S
• G2
Interphase
nucleus
cytoplasm
cytoplasm
• G1 phase, the cell grows
and protein production is
high.
• S phase, DNA is
replicated.
Chromosomes aren’t
visible, since the DNA is
in the form of chromatin.
• The number of
cytoplasmic components
is doubled.
DNA Replication
• “S” stage of Interphase,
DNA must copy itself so
that each new daughter
cell will have its own
copy of the genetic code.
• The two sister
chromatids are held
together by a centromere.
one chromosome (unduplicated)
one chromatid
sister chromatid
one chromosome (duplicated)
CENTROMERE
Chromosome Structure
Kinetochore
Attached to both sides of a
centromere are connecting points
known as kinetochores.
These function as attachment
points for the spindle
microtubules.
One nucleosome
DNA
This diagram shows how DNA wraps around protein
spools known as histones. A histone & its DNA together
are known as a nucleosome.
Mitosis
• The process of the
nucleus dividing is
known as “mitosis”.
• Mitosis has four
stages: Prophase,
Metaphase, Anaphase
and Telophase.
Prophase
The first stage of mitosis is
prophase.
Chromatin condenses and coils
into visible chromosomes.
Nucleolus & nuclear envelope
disintegrate.
EARLY PROPHASE
Spindle apparatus starts to
form between centrioles.
Centrioles (found only in
animal cells) begin moving to
opposite ends of the cell.
LATE PROPHASE
LATE PROPHASE
•
Metaphase
The shortest stage of
mitosis is metaphase.
During this phase, the
sister chromatids are
arranged at the equator
of the cell.
The spindle
microtubules attach to
the kinetochores of each
chromatid.
Anaphase
• During anaphase,
the two sister
chromatids are
separated from each
other by the spindle
microtubules and
moved to opposite
poles.
• Once separated, they
are referred to as
chromosomes, not
chromatids.
Telophase
• The final stage of
mitosis is telophase.
• Chromosomes uncoil
into chromatin.
• Nucleoli & nuclear
envelopes reappear.
• Spindle microtubules
disintegrate.
Cytokinesis
• The division of the
cytoplasm is known
as cytokinesis.
• Cytokinesis is the
final step in the Cell
Cycle.
In animal cells, a
cleavage furrow
forms,
microfilaments
contract and cut
the cell in two.
Cytokinesis
• In plant cells, the cell wall prevents the cell from being
pinched in two.
• Instead, a “cell plate” forms between the two nuclei.
• Cellulose deposits begin to form at the cell plate, forming a
crosswall that divides the parent cell into two daughter
cells.