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Cell Growth and Division
Honors Biology
Chapter 10
Cell Growth
Living things grow larger due to an
increase in cells
Larger the cell, the more demands on the
DNA and the more transport of water and
nutrients across the membrane
The surface area to volume ratio must also
be maintained.
Cell Growth
Before the cell gets too big in size, it must
divide into 2 new daughter cells via a process
known as cell division
In order to divide, the cell must make a copy
of its DNA so each cell has a set of
instructions of how the body functions
DNA Replication
Cell Division
Occurs in 2 main stages
1. mitosis – division of nucleus
2. cytokinesis – division of cytoplasm
Considered to be asexual since the two
daughter cells are genetically identical to
the parent cell
Source of new cells as organism grows
and develops
Chromosomes
Made of DNA and proteins
Cells of every organism have a specific
number of chromosomes
humans = 46 carrot = 18 fruit fly = 8
Chromosomes are only visible during cell
division, these structures form to compact
the DNA to make it easy to divide
Chromosome Structure
Each chromosome consists of 2 identical “sister” chromatids
When the cell divides, the sister chromatids separate from
each other. One chromatid goes to each of the 2 new cells
Each pair of chromatids are attached by the centromere. The
centromere is usually located near the middle of the chromatid
The human body contains 46 chromosomes and 46
centromeres, each of which contain 2 chromatids
Short arm
Long arm
One chromosome with 2
identical sister chromatids
Cell Cycle
During the cell cycle, a cell grows, prepares for
division, and divides to form 2 new identical
daughter cells, each of which then begin the cycle
again.
The cell cycle consists of 4 phases
1. M Phase: (mitosis phase) mitosis and cytokinesis
2. G1 Phase: (gap phase) growth and activity
3. S Phase: (synthesis phase) DNA replication
4, G2 Phase: (gap phase) growth and activity
G1, S and G2 all used to be group together and
called interphase
Cell Cycle G1 Phase
M Phase
S Phase
G2 Phase
Interphase
Cell spends more time in interphase than M
phase
1. G1 Phase – Most growing occurs. Cells
increase in size and synthesize new proteins
and organelles
2. S Phase – Chromosomes are replicated. Key
proteins are synthesized
3. G2 Phase – Shortest of the three phases.
Organelles and molecules required for division
are produced. When the cell completes this
phase it is ready to enter the M phase and begin
the process of cell division
Mitosis
Involves the centrioles (cell organelles made of
proteins and microtubules) of the cell
Occurs in four stages
1. prophase – chromosomes appear and nuclear
envelope breaks down
2. metaphase – chromosomes line up across
center of cell
3. anaphase - sister chromatids separate into
separate cells
4. telophase – chromosomes gather at opposite
ends of two cells and two new nuclear envelopes
begin to form
During Interphase the chromosomes are
Interphase not visible. The cell grows and replicates its
DNA and centrioles
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Prophase
Longest phase of mitosis
Chromatin condenses and chromosomes
become visible
The nuclear envelope begins to break down
Centrioles separate and take positions on
opposite sides of the cell
The spindle, a microtubule structure that helps
separate the chromosomes, begins to form
Prophase
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Metaphase
Chromosomes line up across the center of
the cell.
Microtubules connect the centromere of
each chromosome to the two poles of the
spindle
Metaphase
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Anaphase
The centromeres that join the sister
chromatids of the chromosome split and
allow the sister chromatids to separate
and become individual chromosomes
The chromatids continue to move until
they have separated into two groups near
the poles of the spindle
Anaphase ends when the chromatids stop
moving
Anaphase
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Telophase
Final stage of mitosis
Chromosomes begin to loosen and into a tangle
of dense material
Two new nuclear envelopes begin to reform
around the two clusters of chromosomes
The spindle begins to break apart and a
nucleolus becomes visible in each daughter
nucleus
Mitosis is now complete, 2 nuclei are formed, but
the cells are not yet separated
Telophase
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Cytokinesis
Separation of cytoplasm within a single cell
Typically occurs at the same time as telophase
Cell membrane is drawn inward until the
separation of the cytoplasm into two nearly
equal parts
Each part contains its own nucleus and
organelles
In plants, a cell plate forms midway between the
divided nuclei and a cell wall begins to appear in
the cell plate
Cytokinesis
Spindle
forming
Centrioles
Nuclear Chromatin Centromere Centriole
Chromosomes
envelope
(paired chromatids)
Interphase Prophase Spindle
Cytokinesis Centriole
Individual Metaphase
Telophase chromosomes
Nuclear Anaphase
envelope
reforming
Mitosis and Cytokinesis Video Segment
..\..\bio CD\Chapter 10A.mpg
Did you know????
All of the DNA in an adult human body
could fit inside one ice cube, but if
unwound, stretched out and joined end to
end, it could reach from the earth to the
sun and back again approximately 400
more times.
Homework Assignment
This will be due tomorrow, start it in class
now because it is a long assignment!!!
Suppose you were small enough to hitch a
ride on a chromosome located in an
animal cell that goes through mitosis and
cytokinesis. Describe what you would see
happening during EACH phase of the
process
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