Lesson 16.

Mitosis
 explain how the phases of
Objective 1 mitosis contribute to cell
sAt the end of reproduction; and
the lesson, determine how mitosis
you should be contributes to the maintenance
2 of an organism’s normal
able to:
functions.
 Cell division is the process by which
multicellular organisms produce more cells.
This process is related to the ability of living
organisms to reproduce.
 Learn about It!

Chromosomes
● For a cell to replicate or
divide, it has to double
its contents such as
water, organelles, and
DNA.
Chromosomes consist of the
● A basic characteristic of genetic material of organisms
an organism is its number
of chromosomes.
 Learn about It!

Chromosomes
● A chromosome refers
to a more compressed
and coiled status of
DNA seen during cell
division.
Chromosomes consist of the
● The chromosome is genetic material of organisms
seen as the condensed
version of the
 Learn about It!

Cell Types
● Somatic cells are diploid
cells (with two sets of
chromosomes).

● They function for growth

and various metabolic
activities besides The diploid somatic and
reproduction. haploid sex cells
 Learn about It!

Cell Types
● Sex cells (orgametes),
are meant for
reproduction.

● These are haploid cells,

the sperm cells and egg
cells, that unite during The diploid somatic and
fertilization. haploid sex cells
 Learn about It!

The Cell Cycle

● The cell cycle pertains to
the processes happening
within the cell as it
prepares and executes
cell division.

The cell cycle consists of the

interphase, M phase, and
cytokinesis
 Learn about It!

Interphase
● Interphase is the
longest phase which
makes up 90 percent of
the cell cycle.

● It is when the cell is

active metabolically and
prepares for the process The cell cycle consists of the
of division. interphase, M phase, and
cytokinesis
 Learn about It!

Interphase: G1 Phase
● G1 phase is the stage
when the cell starts to
grow.

● The water content,

enzymes, and organelles
in the cell are doubled.
Majority of growth occurs. The cell cycle consists of the
interphase, M phase, and
cytokinesis
 Learn about It!

Interphase: S Phase
● Synthesis phase allows
an exact copy of the DNA
to be synthesized.

● This is a prerequisite for

cell division so that DNA
copies can be distributed
to the daughter cells. The cell cycle consists of the
interphase, M phase, and
cytokinesis
 Learn about It!

Interphase: G2 Phase
● G2 phase involves the
continuous growth and
preparation division.

● Proteins important the for

chromosome and mitotic
spindle formation are
produced. The cell cycle consists of the
interphase, M phase, and
cytokinesis
 Learn about It!

Interphase: G0 Phase
● G0 phase is a special
phase where the cell is
considered to be in a
resting state (from
division).

● The cell is neither

preparing to divide or is The cell cycle consists of the
currently actively interphase, M phase, and
cytokinesis
 Learn about It!

Checkpoints: G1
● G1 checkpoint primarily
checks for
○ proper cell size
○ adequate nutrients
○ any DNA damage
○ cell growth factors
Checkpoints in cell cycle checks
for various cell conditions
 Learn about It!

Checkpoints: G2
● G2 checkpoint primarily
checks for
○ proper cell size
○ DNA damage from S
phase
● Apoptosis is initiated in
cases of irreplaceable Checkpoints in cell cycle checks
errors. for various cell conditions
 Learn about It!

Checkpoints: Metaphase
● Metaphase checkpoint
checks for
○ proper and equal
separation of these
sister chromatids
○ proper attachment of
spindles Checkpoints in cell cycle checks
for various cell conditions
 Learn about It!

Mitotic Phase
● Mitotic phase or
mitosis involves the
division of the cellular
content. Mitosis has five
stages.

● It is immediately followed
Mitosis is responsible for
by or simultaneously elongating onion root tips
occurs with cytokinesis.
 Learn about It!

Mitotic Phase: Prophase

● Prophase involves the
following events.
○ nuclear disintegration
○ mitotic spindle extends
from the centrosome
○ chromatin condenses
to become visible Prophase is marked by the
chromosomes beginning of chromatin
condensation
 Learn about It!

Mitotic Phase: Prometaphase

● Prometaphase involves
the following events.
○ disappearance of the
nuclear membrane
○ microtubules extend from
centrosomes
○ more condensed Prometaphase is marked by
chromosomes the appearance of
kinetochores
 Learn about It!

Mitotic Phase: Metaphase

● Metaphase involves the
following events.
○ centrosome completely
located on the opposite
poles
○ chromosomes centrally
aligned at metaphase The duplicated chromosomes
plate become centrally located
 Learn about It!

Mitotic Phase: Anaphase

● Anaphase involves the
following events
○ separation of the sister
chromatids
○ single chromosomes
move towards the
opposite poles Spindle fibers shorten to move
the chromosomes to poles
 Learn about It!

Mitotic Phase: Telophase

● Telophase involve the

following events.
○ microtubules detach
from the kinetochore.
○ chromosomes start to
Telophase may happen
uncoil
simultaneously with cytokinesis
 Learn about It!

Cytokinesis
● In animal cells, a
cleavage furrow.

● This furrow starts as a

groove along the cell
membrane’s surface Cleavage furrow formation marks
the animal cell cytokinesis
and then pinches up to
the cell’s center.
 Learn about It!

Cytokinesis
● In plant cells a mass of
cell wall material is
formed called the cell
plate.

● This plate formation Cell plate formation marks the

cytokinesis in plant cells
starts in the middle of
the cell plate and
elongates outwardly.
Key Points

For somatic cells, the cell cycle consists of

interphase and mitosis. Interphase includes the
1 gap 1 phase, synthesis phase, and the gap 2
phase.
The gap phases involve the growth of the cell as
2 it prepares for mitosis. The synthesis phase is
when the genetic material of the cell doubles.
The mitotic phases are prophase,
3 prometaphase, metaphase, anaphase, and
telophase.
 Check Your Understanding

Given that an organism has 10 chromosomes (2N)

before DNA synthesis, how many chromosomes
will the cell have at each of the following?

1. prophase
2. metaphase
3. anaphase
4. telophase
5. cytokinesis
 Challenge Yourself

What will happen to the

daughter cells if the
genetic material does not
migrate to the equatorial
plate? What about if the
genetic material does not
separate during
anaphase?
 Photo Credits
● Slide 17: This file, Onion root mitosis, by staticd, is licensed under CC BY-SA 3.0 via
Wikimedia Commons.
 Bibliography

Bill W. Tillery, et al. 2010. Integrated Science, 4th edition. New York: McGraw-Hill.
Earth Science. USA: CK-12 Foundation, 2009.

Cecie Starr et al. 2014. BIOLOGY: Today and Tomorrow, 4th edition. Singapore: Cengage
Learning Pte Ltd.

Dolores A. Ramirez, Merlyn S. Mendioro, and Rita P. Laude. 2013. Lectures in Genetics, 10th
edition. Genetics and Molecular Biology Division, Institute of Biological Sciences, University
of the Philippines.

Genetic Science Learning Center. "Inventory of Traits". Genetic Science Learning Center,
University of Utah, 2006. Web. 15 Jun. 2018.
<http://learn.genetics.utah.edu/content/basics/activities/pdfs/InventoryOfTraits.pdf>.
 Bibliography

Genetic Science Learning Center. "A Recipe for Traits". Genetic Science Learning Center,
University of Utah, 2008. Web. 15 June. 2018.
<http://learn.genetics.utah.edu/content/basics/activities/pdfs/A%20Recipe%20for
%20Traits_Public.pdf>.

Neil A. Campbell and Jane B. Reece. 2004. Biology, 6th edition. Singapore: Pearson Education
South Asia Pte Ltd.
Neil Campbell, et al. 2013. Biology, 10th edition. Singapore: Pearson Education South Asia Pte
Ltd.

Nolin, Jeanette. "Modeling Mendel’s Pea Experiment". The National Health Museum Activities
Exchange. Web. 15 June. 2018. <
http://www.accessexcellence.org/AE/AEC/AEF/1996/nolin_pea.html>

Wohlwill, Arthur . "Meiosis Introductory Activity". OER Commons. Institute for the
Study of Knowledge Management in Education, 24 Oct. 2016. Web. 07 Jun.
2018.https://www.oercommons.org/authoring/17535-meiosis-introductory-activity>.