Cell Division: Mitosis, The Great Divide

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Sharp Tutor Thu, Jan 27, 2022 08:28 AM UTC

We will be discussing why would a cell divide and a closer look at cell division or Mitosis. In cell biology, mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained.

1. The Great Divide
05/04

2. Why Would a Cell Divide?
 As cells absorb nutrients and get larger,
the volume of the cell increases faster
than the surface area
 This means that a cell can no longer
absorb nutrients and get rid of wastes
fast enough to support its demands
(volume)
 So what’s a cell to do? DIVIDE !!!!

3. Why Would a Cell Divide?
Besides growth a cell would also divide
for:
 Repair or Replacement
 Cancer
Different cells divide at different rates:
 Most mammalian cells = 12-24 hours
 Some bacterial cells = 20-30 minutes

4. Getting Older…
 All cells are only allowed to complete a
certain number of divisions
 Then they die (programmed cell death)
How does cell division change over a lifetime?
 Childhood = cell division > cell death
 Adulthood = cell division = cell death
 The Later Years = cell division < cell
death

5. Cell Cycle Tidbits
How long is one cell cycle?
 Depends on the cell- skin cells =
~24 hours, nerve cells = never
after maturity, cancer cells =
very short
 Remember: every cell only has a
certain # of divisions it can
undergo, then it dies = apoptosis
(programmed cell death)

6. The Cell Cycle

7. Stages of the Cell Cycle
There are two stages to a cells
life.
interphase (growth & replication of DNA)
mitotic phase (division of cell into 2
daughter cells)
 Cell spends
about 90% of
the time in
interphase

8. Interphase
 Divided into 3 phases:
 G1 (1st gap) = small cell is absorbing
nutrients, growing & doing its job.
 S (synthesis) = cell is continuing to
grow & duplicates its DNA.
 G2 (2nd gap) = cell keeps growing &
doing its job.

9. Mitosis: A Closer Look
DNA is all twisted up
into a Chromosome.
 During S phase the
Chromosome is
copied.
 2 complete identical
sets of
chromosomes.
 They are connected
in the middle by a
centromere.
 A single copied
chromosome is

10. The Mitotic Phase
 Divided into 4 stages of Mitosis:
 Prophase
 Metaphase
 Anaphase
 Telophase
(+) PLUS
 Cytokinesis

11. Prophase
 Chromatids condense
becoming visible.
 Nuclear membrane
dissolves
 The centrioles (an
organelle that makes
microtubules) appears
and migrate to opposite
sides.
 spindle fibers start to
 form between them
http://www.biostudio.com/demo_freeman_dna_coiling.htm

12. Metaphase
 Chromosomes
line-up on the
metaphase
plate
 Centromeres
are attached
to spindle
fibers

13. Anaphase
 Spindle fibers
contract
 Centromeres divide
 Sister chromatids
are pulled away
from each other
towards the poles

14. Telophase
 The
chromosomes
reach the poles
 Nuclear
membranes
form around
the 2 new
nuclei

15. Cytokinesis
 The cytoplasm
distributed Animal Plant
equally between
the 2 new cells
 In animals, a
cleavage furrow
forms from
outside in
 In plants, a cell
plate forms from

16. What Mitosis Actually Looks Like
Interphase
Prophase Metaphase
Telophase
Anaphase

17. What Happens After Mitosis?
 The cell
returns to
interphase
 Chromosom
es uncoil
back into
chromatin
 The cycle
repeats
itself over &

18. At What Stage Are Our Cells At In The Cell Cycle?
 Different cells
can be in
different stages
 Interphase
 Mitosis:
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis

19. The Guarentee
 The product of
mitosis is 2 cells Moth
er cell
 The daughter
cells are
identical to each
other & to the
Identical
mother cell daughter
cells
Why is this so
important?

20. The Daughter Cells
 In humans, the 2
daughter cells will
have 46
chromosomes (23
pairs)
 Each chromosome is
said to have the Identical
same gene daughter
cells
sequence

21. The Beauty of Asexual Reproduction
 Mitosis is a
form of Moth
er cell
asexual
reproduction
Runners produces by
strawberries
 New
individuals
Identical
are Budding by hydra & yeast
daughter
produced by cells
1 parent &
thus, are Cuttings from plants
identical to

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