Download Unit 3 Interphase and Mitosis Notes

UNIT 3 NOTES
INTERPHASE AND MITOSIS
New cells are produced by division
of existing cells.
If many new cells are needed, cells
go through a cycle of events again
and again - this is called the cell
cycle.
The cell cycle describes the behavior
of cells as they grow and divide.
Cytokines
is
DNA
Synthesis/Re
plication
Interphase
Interphase is the largest and longest part
of the cell cycle
Includes 3 phases: G1, S, and G2
Interphase
Phases
G1
S
Major Events
Growth of cell and increase # of
organelles
Replication/copying of chromosomes =
DNA Synthesis
More growth, increase # of organelles,
Interphase is a very active time in a
cell's life.
It involves chemical reactions, DNA
replication, and an increase in the
number of organelles.
More mitochondria and in plants,
more chloroplasts
Because interphase involves
growth, it is essential that protein
Question: Which of the following does
not occur during interphase?
A. DNA Replication
B. Growth
C. Cytokinesis
D. An increase in the number of
mitochondria
Answer: C, cytokinesis
Question: Which events occur during
the G1 and S phases of the cell cycle?
G1 Phase
S Phase
A
DNA replicates
cell grows
B
mitosis begins
cell divides
C
cell divides
mitosis begins
D
cell grows
DNA replicates
Answer: D
Question: During which phase of the
cell cycle do chromosomes duplicate?
A. G1
B. S
C. G2
D. Mitosis
Answer: B, S phase
ell Cycle has 3 stages:
Interphase
Mitosis (division of the nucleus)
Cytokinesis (division of cytoplasm)
I
PMAT
C
At the end of interphase, the cell begins
mitosis - the process by which the nucleus
divides to form 2 genetically identical nuclei.
After mitosis is completed, the cytoplasm of
the cell starts to divide - known as
cytokinesis.
Eventually 2 cells are formed, each
containing 1 nucleus.
These cells are identical, called daughter
cells
The 2 cells begin interphase when
1 chromosome
= 2 sister
chromatids
Sister
chromatids
are identical
Centromere
holds sister
chromatids
During G2, chromatin (elongated/relaxed
DNA) begins to condense via a process
called supercoiling.
First the DNA wraps around histones
(proteins) and a final coiling occurs to
produce the chromosome - now ready for
4
Phases
in
Mitosis
1. Prophase
Chromatin condense to become tightly
coiled chromosomes.
Nucleolus and nuclear membrane start to
disappear.
Spindle fibers begins to form.
Centrosomes move toward opposite poles of
the cell due to lengthening of microtubules.
These centrosomes are what spindle fibers
are attached to.
PROPHASE
2. Metaphase
All chromosomes move to the middle or
equator of the cell.
Chromosome's centromeres line up in
the middle.
Movement of the chromosomes is due
to the action of the spindle which is
made of microtubules.
Centrosomes are now at the opposite
METAPHASE
3. Anaphase
Begins when the 2 sister chromatids of each
chromosome are split.
These chromatids, now called daughter
chromosomes, move toward the opposite poles
of the cell.
The chromatid movement is due to shortening
of the spindle fibers.
At the end of Anaphase, each pole of the cell
has a complete, identical set of chromosomes,
ANAPHASE
4. Telophase
Chromosomes are now completely at
opposite poles.
Spindle fibers disappear and a new
nuclear membrane begins to re-form
around each set of chromosomes.
In animals, the pinching of the
cytoplasm is called the cleavage
furrow, and in plants it is the cell plate.
TELOPHASE
Cytokinesis
Once nuclear division has occurred, the
cell undergoes cytokinesis.
cell division = mitosis + cytokinesis
Both processes result in 2 daughter cells
with genetically identical nuclei.
CYTOKINESIS
Question:
2.
3.
1.
8.
5.
6.
7.
4.
Question: What is the sequence of
stages during the cell cycle?
A. G1→S→G2→mitosis→cytokinesis
B. mitosis→G1→G2→cytokinesis→S
C. G1→G2→S→mitosis→cytokinesis
D. G1→G2→mitosis→cytokinesis→S
Answer: A
Questions: Which of the following take(s) place
during interphase and mitosis?
I. Re-formation of nuclear membranes
II. Chromosomes pairing up
III. DNA replication
A. I only
C. II and III only
B. I and II only
D. I and III only
Answer: D, I and III only
Question: Diagram below shows a cell
during mitosis
A
B
C
D
Stage of mitosis
metaphase
anaphase
anaphase
metaphase
Answer: D
Structure I
Structure II
chromatid nuclear membrane
centromere
cell membrane
chromatid nuclear membrane
centromere
cell membrane
Homework: Remember, quiz
1.
At
one
time,
interphase
was
referred
to
as
tomorrow!
the resting phase of the cell cycle. Why is this
no longer used?
2. If a parent cell has 20 chromosomes, how
many chromatids would be present during
metaphase of mitosis?
3. Name the stages of the cell cycle that
precedes mitosis and follows mitosis.
4. State 3 uses of mitosis in plants and
animals.