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Chapter 4
Cancer
DNA Synthesis, Mitosis, and Meiosis
Fourth Edition
BIOLOGY
Science for Life | with Physiology
Colleen Belk • Virginia Borden Maier
© 2013 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
PowerPoint Lecture prepared by
Jill Feinstein
Richland Community College
1 What Is Cancer?
 Tumor: Unregulated cell division that form a mass
of cells with no function
 Benign tumor: doesn’t affect surrounding
tissues
 Malignant tumor: invades surrounding tissues;
cancerous
 Metastasis: cells break away from a malignant
tumor and start a new cancer at another
location
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1 What Is Cancer?
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1 What Is Cancer?
 Metastatic cells can travel throughout the body
via the circulatory system or the lymphatic
system.
 Once in either system the cancer cells can travel
anywhere in the body
 Cancer cells differ from normal cells:
 Divide when they shouldn’t
 Invade surrounding tissues
 Move to other locations in the body
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1 What Is Cancer?
 Risk factors: increase a person’s risk of developing
a disease (Table 6.1)
 Tobacco use: tobacco contains many carcinogens
 Alcohol consumption
 High-fat, low-fiber diet
 Lack of exercise
 Obesity
 Increasing age which weakens the immune system
 Cells that divide frequently such as ovarian cells
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2 Passing Genes and Chromosomes to Daughter
Cells
 Asexual reproduction:
 Only one parent
 Offspring are genetically identical to parent
 Sexual reproduction
 Gametes are combined from two parents
 Offspring are genetically different from one another
and from the parents
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2 Passing Genes and Chromosomes to Daughter
Cells
 Before dividing, cells must copy their DNA
 Gene: section of DNA that has the instructions for
making all proteins
 One molecule of DNA is wrapped around proteins to
form a chromosome containing hundreds of genes.
 Different species have different numbers of
chromosomes (we have 46).
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2 Passing Genes and Chromosomes to Daughter
Cells
 Chromosomes are uncondensed before cell division
 Duplicated chromosomes, held together at the
centromere, are called sister chromatids
 They are duplicated through DNA replication
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2 Passing Genes and Chromosomes to Daughter
Cells
 DNA molecule is a double stranded structure similar
to a twisted ladder.
 The sides of the ladder are composed of a sugarphosphate backbone.
 Nucleotides are connected to each other by
hydrogen bonding to form the “rungs” of the ladder.
 Adenine (A) pairs with thymine (T)
 Cytosine (C) pairs with Guanine (G)
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2 Passing Genes and Chromosomes to Daughter
Cells
 DNA molecule is split up the
middle of the helix
 Nucleotides are added to each
side via hydrogen bonding
 Result is two identical daughter
molecules, each with one parental
strand and one new strand
(semiconservative replication)
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2 Passing Genes and Chromosomes to Daughter
Cells
 DNA polymerase:
the enzyme that
replicates DNA
 It moves along
the length of the
unwound DNA
and helps form
the new strands
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2 Passing Genes and Chromosomes to Daughter
Cells
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BioFlix: DNA Replication
Animation: The Structure of DNA
Click “Go to Animation” / Click “Play”
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3 The Cell Cycle and Mitosis
 Cell cycle has three steps:
 Interphase: the DNA replicates
 Mitosis: the copied chromosomes are moved into
daughter nuclei
 Mitosis occurs in somatic or body cells.
 Cytokinesis: the cell is split into 2 daughter cells
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3 The Cell Cycle and Mitosis - Interphase
 Interphase has three phases:
 G1: cell grows, organelles duplicate
 S: DNA replicates
 G2: cell makes proteins needed to complete
mitosis
 Most of the cell cycle is spent in interphase
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Animation: The Cell Cycle
Click “Go to Animation” / Click “Play”
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3 The Cell Cycle and Mitosis - Mitosis
 Mitosis produces genetically-identical daughter
nuclei
 Mitosis is followed by cytokinesis which splits the
two nuclei into two daughter cells
 Four stages:
 Prophase
 Metaphase
 Anaphase
 Telophase
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3 The Cell Cycle and Mitosis - Mitosis
 Prophase:
 Chromosomes condense
 Nuclear envelope disappears
 Microtubules pull the chromosomes around during
cell division
 Animal cells: microtubules attached to centrioles at
the poles of the cell
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3 The Cell Cycle and Mitosis - Mitosis
 Metaphase:
 Chromosomes are aligned across the middle of the
cell by microtubules
 Anaphase:
 centromeres split,
 sister chromatids are pulled apart toward opposite
poles
 Telophase:
 Nuclear envelopes reform around chromosomes
 Chromosomes revert to uncondensed form
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3 The Cell Cycle and Mitosis - Mitosis
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3 The Cell Cycle and Mitosis - Mitosis
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BioFlix: Mitosis
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Animation: Mitosis
Click “Go to Animation” / Click “Play”
3 The Cell Cycle and Mitosis - Cytokinesis
 Cytokinesis is the stage in which two daughter
cells are formed from the original one
 After cytokinesis, cells reenter interphase.
 Animals:
 Proteins pinch the original cell into two new cells
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3 The Cell Cycle and Mitosis - Cytokinesis
 Cytokinesis in Plants:
 Starts with vesicles forming the cell plate.
 This results in a new cell wall being formed
between the cells forming daughter cells.
 The cell wall is made from cellulose
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4 Cell Cycle Control and Mutation
 Cell division is a tightly controlled process
 Normal cells halt at checkpoints
 Proteins survey the condition of the cell
 Cell must pass the survey to proceed with cell
division
 3 checkpoints: G1,G2, and metaphase
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4 Cell Cycle Control and Mutation
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4 Cell Cycle Control and Mutation
 Growth factors stimulate cells to divide
 Growth factors bind to receptors to trigger a
response from a cell
 Mutation: a change in the sequence of DNA
 Changes to DNA can change the structure and
function of the protein coded by the DNA
 Mutations may be inherited or caused by carcinogens
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4 Cell Cycle Control and Mutation
 Proto-oncogenes: genes that code for the cell cycle
control proteins
 When proto-oncogenes mutate, they become
oncogenes
 Their proteins no longer properly regulate cell division
 They usually overstimulate cell division
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4 Cell Cycle Control and Mutation
 Tumor suppressor genes: genes for proteins that
stop cell division if conditions are not favorable
 When mutated, can allow cells to override
checkpoints
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4 Cell Cycle Control and Mutation
 Depending on the number of mutations and whether
the tumor suppressor protein is functional will
determine whether it is a benign or malignant tumor
that is formed.
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4 Cancer Development Requires Many Mutations
 Progression from benign tumor to cancer requires
many mutations.
 Angiogenesis: tumor gets its own blood supply
 Loss of contact inhibition: cells will now pile up
on each other
 Loss of anchorage dependence: enables a
cancer cell to move to another location
 Immortalized: cells no longer have a fixed number
of cell divisions due to an enzyme called
telomerase
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4 Cell Cycle Control and Mutation – Multiple Hit
Model
 Multiple hit model: process of cancer development
requires multiple mutations
 Some mutations may be inherited (familial risk)
 Most are probably acquired during a person’s
lifetime
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5 Cancer Detection and Treatment
 Early detection increases odds of survival
 There are different detection methods for
different cancers
 Some cancers produce increased amount of a
characteristic protein
 Biopsy: surgical removal of cells or fluid for
analysis
 Needle biopsy: removal is made using a needle
 Laparascope: surgical instrument with a light,
camera, and small scalpel
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5 Cancer Detection and Treatment - Treatment
Methods
 Chemotherapy: drugs that selectively kill dividing
cells
 Combination of different drugs used (“cocktail”)
 Interrupt cell division in different ways
 Helps prevent resistance to the drugs from arising
 Normal dividing cells are also killed (hair follicles,
bone marrow, stomach lining)
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5 Cancer Detection and Treatment - Treatment
Methods
 Radiation therapy: use of high-energy particles to
destroy cancer cells
 Damages their DNA so they can’t continue to divide
or grow
 Usually used on cancers close to the surface
 Typically performed after surgical removal of tumor
 If a person remains cancer free after treatment for 5
years they are in remission and after 10 years they
are cured.
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6 Meiosis
 Specialized form of cell
division in gonads to
produce gametes
 Reduces number of
chromosomes in each
cell by one-half
 Chromosomes come
in homologous pairs
 Gamete gets one of
each pair
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6 Meiosis
 Chromosomes can be visualized using a
karyotype.
 Human somatic cells have 22 pairs of autosomes
and one pair of sex chromosomes
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6 Meiosis
 Gametes are haploid or have 1 set of 23
chromosomes
 When the egg and sperm nuclei fuse it forms a
zygote which is diploid
 Somatic or body cells are also diploid
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6 Meiosis
 Starts with interphase – DNA is duplicated
 Meiosis takes place in two stages:
 Meiosis I
 Separating out the homologous pairs into 2 separate
cells
 Meiosis II
 Separating out the sister chromatids in each cell to
produce 4 haploid cells.
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6 Meiosis I
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6 Meiosis II
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6 Meiosis
 Crossing over: exchange of equivalent portions of
chromosomes between members of a homologous
pair
 Results in new types of gametes being formed
 Linked genes typically cross over together
 Random alignment: the way in which different
pairs of chromosomes align and get separated
during meiosis I is random
 Results in different types of games being formed
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BioFlix: Meiosis
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Animation: Meiosis
Click “Go to Animation” / Click “Play”
6 Meiosis - Mistakes in Meiosis
 Nondisjunction: failure of homologues to separate
normally during meiosis
 Results in a gamete having one too many
chromosomes (trisomy) or one too few
chromosomes (monosomy)
 Most embryos that result from such gametes will die
before birth
 Several chromosome abnormalities are known in
humans (Table 6.2)
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6 Comparison of Mitosis and Meiosis
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6 Meiosis
 For cancer mutations to be passed on to offspring,
they must take place in cells that give rise to
gametes.
 Mutations caused by environmental exposures are
not passed on unless the mutation occurs in the
gametes.
 Mutations in somatic cells (e.g., skin cancer from UV
ray exposure) are not heritable.
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Which of following statements incorrectly identifies
how cancer cells differ from normal cells?

Cancer cells divide when they should not.

Cancer cells invade surrounding tissues.

Cancer cells form benign tumors.

Cancer cells can move to other locations in
the body.
© 2013 Pearson Education, Inc.
Which of following statements incorrectly identifies
how cancer cells differ from normal cells?

Cancer cells divide when they should not.

Cancer cells invade surrounding tissues.

Cancer cells form benign tumors.

Cancer cells can move to other locations in
the body.
© 2013 Pearson Education, Inc.
How many chromosomes does a human body cell
contain?

12

23

34

46
© 2013 Pearson Education, Inc.
How many chromosomes does a human body cell
contain?

12

23

34

46
© 2013 Pearson Education, Inc.
Which statement correctly describes the role of
DNA polymerase in DNA replication?

DNA polymerase splits the double-stranded DNA
in half.

DNA polymerase helps bind incoming nucleotides
to each other.

DNA polymerase lines up chromosomes on the
metaphase plate.

DNA polymerase helps prevent the degradation
of chromosomes.
© 2013 Pearson Education, Inc.
Which statement correctly describes the role of
DNA polymerase in DNA replication?

DNA polymerase splits the double-stranded DNA
in half.

DNA polymerase helps bind incoming
nucleotides to each other.

DNA polymerase lines up chromosomes on the
metaphase plate.

DNA polymerase helps prevent the degradation
of chromosomes.
© 2013 Pearson Education, Inc.
During which phase of mitosis does the
centromere split, allowing motor proteins to pull
each sister chromatid to opposite poles of the cell?

prophase

metaphase

telophase

anaphase
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During which phase of mitosis does the
centromere split, allowing motor proteins to pull
each sister chromatid to opposite poles of the cell?

prophase

metaphase

telophase

anaphase
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A gene encoding a protein that regulates the G1
checkpoint is mutated What is a likely outcome?

Tumors will develop.

The cell will die.

The cell will live but never divide.

The cell will become larger and large.
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A gene encoding a protein that regulates the G1
checkpoint is mutated What is a likely outcome?

Tumors will develop.

The cell will die.

The cell will live but never divide.

The cell will become larger and large.
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The genes that encode the proteins regulating the
cell cycle are called ________.

oncogenes

proto-oncogenes

carcinogens

malignant
© 2013 Pearson Education, Inc.
The genes that encode the proteins regulating the
cell cycle are called ________.

oncogenes

proto-oncogenes

carcinogens

malignant
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True or False: Chemotherapy causes hair loss
because hair follicles divide rapidly, like cancer
cells.

True

False
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True or False: Chemotherapy causes hair loss
because hair follicles divide rapidly, like cancer
cells.

True

False
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At what stage of meiosis does crossing
over occur?

metaphase I

metaphase II

prophase I

prophase II
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At what stage of meiosis does crossing
over occur?

metaphase I

metaphase II

prophase I

prophase II
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A checkpoint is missing from this picture. Where is
this checkpoint?

at the beginning of G2

at the end of M phase

during S phase

at the end of G2
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A checkpoint is missing from this picture. Where is
this checkpoint?

at the beginning of G2

at the end of M phase

during S phase

at the end of G2
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What does this figure show?

centromere

karyotype

cancerous cells

animal cells of
different sizes
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What does this figure show?

centromere

karyotype

cancerous cells

animal cells of
different sizes
© 2013 Pearson Education, Inc.