Transcript Document

ESSENTIAL QUESTION:
WHAT ARE THE FOUR
STAGES OF MITOSIS?
THINK-PAIR-SHARE

Why are cells small? Why would it be bad for
them to grow too large?
CELL CYCLE RE-CAP
1.
2.
3.
4.

G1
S phase
G2
M phase
Remember that G1, S, and G2 together are known as
interphase and a cell spends most of it’s life in
interphase.
REASONS FOR CELL DIVISION
1.
To prevent them from being inefficient in getting
nutrients

2.
To reproduce

3.
For example: bacteria can reproduce asexually
To repair damaged tissue

4.
surface area to volume ratio
For example: if you get a paper cut
To grow an organism
MITOSIS IN THE CELL
There are many words that
describe DNA in it’s
various forms…
A. DNA is usually found as
chromatin while the cell
is doing its normal job.
1. Chromatin is the
granular material visible
within the nucleus that
consists of DNA tightly
coiled around proteins.
B. BEFORE A
CELL DIVIDES,
CHROMATIN
(DNA) COILS UP
TO FORM
CHROMOSOMES.
1.CHROMOSOMES
ARE MADE UP OF
DNA AND
PROTEINS.
2. ALL ORGANISMS
DO NOT HAVE THE
SAME NUMBER OF
CHROMOSOMES.
3. HUMAN CELLS
HAVE 46
CHROMOSOMES.
4. CHROMOSOMES
ARE ONLY VISIBLE
DURING CELL
DIVISION.
C. BEFORE EACH
CELL DIVISION,
EACH
CHROMOSOME IS
REPLICATED, OR
COPIED.
D. FOR THIS
REASON, EACH
CHROMOSOME
CONSISTS OF TWO
IDENTICAL SISTER
CHROMATIDS.
E. EACH PAIR OF
SISTER
CHROMATIDS IS
ATTACHED AT AN
AREA CALLED THE
CENTROMERE.
A HUMAN BODY
CELL ENTERING
CELL DIVISION
CONTAINS 46
CHROMOSOMES OR
92 CHROMATIDS.
NOW LET’S TALK ABOUT MITOSIS… II. THE TWO
MAIN STAGES OF CELL DIVISION ARE MITOSIS
AND CYTOKINESIS.
Cyto
= Cell
Kinesis =
Movement
A. THE FIRST
STAGE,
DIVISION OF
THE CELL
NUCLEUS, IS
CALLED
MITOSIS.
B. THE
SECOND STAGE,
DIVISION OF
THE
CYTOPLASM, IS
CALLED
CYTOKINESIS.
C. REPRODUCTION
BY MITOSIS IS
CLASSIFIED AS
ASEXUAL.
1. UNICELLULAR
ORGANISMS
REPRODUCE IN THIS
MANNER.
2. MITOSIS IS
ALSO THE SOURCE
OF NEW CELLS
WHEN A
MULTICELLULAR
ORGANISM GROWS
AND DEVELOPS.
D. AS YOU REMEMBER, A CELL SPENDS MOST OF ITS
TIME IN INTERPHASE. DURING INTERPHASE, A CELL
DOES ITS NORMAL JOB, GROWS LARGER, COPIES ITS
DNA, AND PREPARES FOR CELL DIVISION.
DRAW THIS!
III. MITOSIS
A. BIOLOGISTS
DIVIDE THE
EVENTS OF
MITOSIS INTO
PHASES:
PROPHASE,
METAPHASE,
ANAPHASE,
AND
TELOPHASE
(PMAT).
4
DURING PROPHASE, THE CHROMOSOMES BECOME
VISIBLE, THE CENTRIOLES SEPARATE TO OPPOSITE SIDES
OF THE CELL, THE CHROMOSOMES ATTACH TO THE
SPINDLE, THE NUCLEOLUS DISAPPEARS, AND THE
NUCLEAR ENVELOPE BREAKS DOWN.
DRAW THIS!
B. THE CENTRIOLES
ARE TWO TINY
STRUCTURES LOCATED
IN THE CYTOPLASM
NEAR THE NUCLEAR
ENVELOPE THAT HELP
ORGANIZE THE
SPINDLE.
C. THE SPINDLE
FIBERS ARE A FANLIKE
MICROTUBULE
STRUCTURE THAT
HELPS SEPARATE THE
CHROMOSOMES.
DURING METAPHASE, THE
CHROMOSOMES LINE UP
ACROSS THE CENTER OF
THE CELL (MIDDLE).
DURING ANAPHASE, THE
CENTROMERES THAT JOIN
THE SISTER CHROMATIDS
SPLIT AND THE
CHROMOSOMES MOVE
UNTIL THEY HAVE
SEPARATED INTO TWO
GROUPS NEAR THE POLES
OF THE SPINDLE (AWAY).
DRAW THIS!
DURING TELOPHASE, THE CHROMOSOMES BEGIN
TO DISPERSE INTO A TANGLE OF DENSE
MATERIAL, THE NUCLEAR ENVELOPE REFORMS
AROUND EACH CLUSTER OF CHROMOSOMES, THE
SPINDLE BREAKS APART, AND THE NUCLEOLUS
BECOMES VISIBLE IN EACH NUCLEUS.
DRAW THIS!
Always remember…
P
M A
PROPHASE
METAPHASE
TELOPHASE
ANAPHASE
T
D. CELL DIVISION IS NOT COMPLETE AFTER
TELOPHASE.
CYTOKINESIS IS DIVISION OF THE CYTOPLASM.
IN ANIMAL CELLS, CYTOKINESIS OCCURS WHEN THE CELL
MEMBRANE IS DRAWN INWARD UNTIL THE CYTOPLASM IS
PINCHED INTO TWO EQUAL PARTS.
IN PLANT CELLS, CYTOKINESIS OCCURS WHEN A CELL PLATE
FORMS CLEAVAGE FURROW BETWEEN THE DIVIDED NUCLEI
GRADUALLY DEVELOPING INTO A SEPARATING MEMBRANE.
MITOSIS IN THE CELL
LET’S PRACTICE…

On the back of your page, number 1-5.

On the next slide, you will see 5 pictures.

You need to figure out what phase each one is in
and write it down.
1
2
4
3
5