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Class Notes
Cellular Reproduction
Chapter 9: p. 244-257
And Inside the Cell p. 48-51
Questions/Main Idea:
Why is there a limit on cell
size?
What is the cell cycle?
Name: _______________________________________
Period:_______________________________________
Date: _______________________________________
Notes:
The ratio of surface area (cell membrane) to volume (cytoplasm and organelles) is
important. In small cells, it is easier for nutrients and waste products to move to their
appropriate location. In larger cells, there would be difficulty supplying necessary
substances throughout the cell, and transporting substances throughout the cell.
(ex. Is it easier for a ping pong ball to move across a bucket of water or a swimming
pool?)
Define the 3 main phases of the cell cycle:
Interphase- Cell grows, carries out cell functions, replicates (copies) DNA
Mitosis – Cell’s nucleus and nuclear material divides
Cytokinesis - The cell’s cytoplasm divides, creating a new cell
What happens during
Interphase?
G1 – period immediately after a cell divides. The cell grows and carries out normal
cell functions, preparing for DNA replication
S - Synthesis – Cell copies its DNA in preparation for cell division (“Replication”)
G2 – Cell prepares for the division of its nucleus. Proteins that make microtubules for
cell division are made, and the cell checks itself to make sure it’s ready to continue the
next stage of division (ex. replicated DNA is checked for errors)
What is the difference
between chromosomes and
chromatin?
What is the name of
the method
prokaryotic cells
use to divide?
Define sister chromatid and
centromeres:
Chromosomes – Condensed form of DNA, the genetic material that is passed from
generation to generation of cells.
Chromatin- Relaxed form of DNA during interphase, which allows for DNA to
replicate
Binary Fission
Sister chromatid- each half of the X-shaped chromosome is an identical copy of
that chromosome’s DNA.
Centromere- the structure at the center where the sister chromatids are attached
For each of the following
stages of mitosis, describe
what happens, and draw a
diagram:
PROPHASE
In prophase, the longest stage of mitosis:
 chromatin condenses into X-shaped chromosomes (containing 2 identical
sister chromatids).
 The nucleolus disappears.
 The nuclear membrane disintegrates and the
 The spindle apparatus begins to form. The spindle apparatus includes spindle
fibers, centrioles (in animal cells), and aster fibers. The spindle apparatus is
important in moving chromosomes, to ensure that each new cell receives a
complete copy of the DNA.
METAPHASE
In metaphase, one of the shortest phases of mitosis:
 Sister chromatids are pulled by motor proteins along the spindle apparatus
towards the middle of the cell
 Sister chromatids line up along the equator
ANAPHASE
In anaphase, the chromatids are pulled apart:
 The microtubules of the spindle apparatus shorten, which pulls at the
centromere of each sister chromatid, causing them to separate into 2 identical
chromosomes.
 The chromosomes move toward the poles of the cell (opposite sides)
TELOPHASE
The last stage of mitosis is telophase.
 Chromosomes arrive at the poles and begin to relax or deconsense
 2 new nuclear membranes begin to form
 Nucleoli reappear
 Spindle apparatus breaks down and parts are recycled to build the
cytoskeleton
Nucleus has divided, but cell division is not yet complete
CYTOKINESIS
Cytoplasm and all other cell contents divide, resulting in 2 identical cells
How does a cell regulate its
cycle?
How is cancer a result of an
uncontrolled cell cycle?
What are carcinogens?
What is Apoptosis?
What are stem cells?
Unspecialized cells that can
develop into specialized cells

Proteins (cyclins and CDKs) regulate the cell cycle by controlling the start
and end of various activities within the cell
 Quality control checkpoints monitor the cycle and can stop it if something
goes wrong. Ex. Check DNA for mistakes before replication, check for
mistakes after replication
Cancer is uncontrolled growth and division of cells – a failure in the regulation of the
cell cycle.
Cancer cells can crowd out normal cells
Carcinogens are agents that are known to cause cancer
Apoptosis is programmed cell death
Examples:
 cells between fingers and toes during development of hands and feet
 cells in the leaves that fall in autumn
 Damaged cells (like sunburned skin)
Embryonic Stem Cells – after a sperm fertilizes an egg, the cells divide repeatedly
until there about 150 cells which have not become specialized yet. Each can develop
into many various types of cells. Embryonic stem cell research is controversial
because of ethical concerns about the source of the cells.
Adult Stem Cells – found in various tissues, might be used to repair the same kind
of tissue in which they are found. They might be able to develop into different types of
cells, or used in treatments of diseases. Less controversial because the cells can be
obtained with the consent of their donors.
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