Download BSC1005 /Belk_Chapter 5

Chapter 5
Cancer
DNA Synthesis, Mitosis, and Meiosis
PowerPoint lecture prepared by
Steve McCommas
Southern Illinois State University
Copyright © 2010 Pearson Education, Inc.
What is Mitosis?
 Mitosis
 Takes one cell and produce two cells
that are the genetic equivalent of the
parent.
 Mitosis is nuclear division. It is the
process by which a new cell receives
the identical DNA as its parent cell
 The new cell is called the daughter cell.
Mitosis produces two identical daughter
cells
Copyright © 2010 Pearson Education, Inc.
How do you get to be 6 ft tall if you
started out as a single cell?
How do you heal a wound?
How do you replace worn out cells?
Copyright © 2010 Pearson Education, Inc.
Why is mitosis important?
 This is how multicellular organisms
grow, repair or heal injuries and
maintain function.
 It is also how asexual reproduction
takes place
Copyright © 2010 Pearson Education, Inc.
5.1 What Is Cancer?
 Unregulated cell division (mitosis out of
control)
 Tumor: mass of cells with no function
Tumor
Normal
cell
Normal cell division
Copyright © 2010 Pearson Education, Inc.
Potentially
cancerous
cell
Unregulated cell division
Malignant
if tumor invades
surrounding tissue
(cancerous)
Benign
if tumor has no
effect on
surrounding tissue
(noncancerous)
Metastatic
if individual cells break
away and start a new
tumor elsewhere
(cancerous)
Figure 5.2
5.1 What Is Cancer?
 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
Tumor
Normal
cell
Normal cell division
Copyright © 2010 Pearson Education, Inc.
Potentially
cancerous
cell
Unregulated cell division
Malignant
if tumor invades
surrounding tissue
(cancerous)
Benign
if tumor has no
effect on
surrounding tissue
(noncancerous)
Metastatic
if individual cells break
away and start a new
tumor elsewhere
(cancerous)
Figure 5.2
Fig. 12.17
Copyright
© 2002
PearsonInc.
Education,
Copyright
© 2010 Pearson
Education,
Inc., publishing as Benjamin Cummings
5.1 What Is Cancer?
 Metastatic cells can travel throughout the
body via the circulatory system or the
lymphatic system.
 Lymphatic system collects fluid that leaks
from capillaries.
 Lymph nodes filter the lymph.
 Cancer cells found in lymph nodes indicate
metastasis has taken place.
Copyright © 2010 Pearson Education, Inc.
5.1 What Is Cancer? How are cancer cells
different from normal cells?
 Cancer cells differ from normal cells:
 Divide when they shouldn’t
 Invade surrounding tissues
 Move to other locations in the body
Copyright © 2010 Pearson Education, Inc.
5.1 What Is Cancer?
 Risk factors: increase a person’s risk of
developing a disease
 Tobacco use: tobacco contains many
carcinogens (chemicals that can cause
cancer)
 Alcohol consumption: alcohol and tobacco
increase risk in multiplicative manner
 High-fat, low-fiber diet
Copyright © 2010 Pearson Education, Inc.
5.1 What Is Cancer? - Risk factors
 Lack of exercise increases risk in two
ways
 Exercise keeps immune system healthy
 Exercise helps prevent obesity
 Increasing age
 Immune system declines with age
 Cumulative damage
 Cells that divide frequently
Copyright © 2010 Pearson Education, Inc.
5.2 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
Copyright © 2010 Pearson Education, Inc.
What must happen before mitosis?
 The cell must make exact copies of its
chromosomes in the nucleus so each
new daughter cell gets the same
number and type of chromosomes as
its parent cell
 A chromosome is a package of genes
and it is made up of DNA.
Copyright © 2010 Pearson Education, Inc.
5.2 Passing Genes and Chromosomes to
Daughter Cells
 Before dividing, cells must copy their DNA
 Gene: section of DNA that has the instructions
for making one protein
 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).
What is a chromosome?
What is a gene?
What is our chromosome species number?
Copyright © 2010 Pearson Education, Inc.
5.2 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
A
A
b
A
b
b
Centromere
Replication
Sister
chromatids
Unduplicated
chromosome
Copyright © 2010 Pearson Education, Inc.
C
C
C
Duplicated
chromosome
Figure 5.6
chromosome (unduplicated)
in a cell at interphase
same chromosome (duplicated)
in interphase prior to mitosis
mitosis, cytoplasmic division
chromosome (unduplicated)
in a daughter
cell at interphase
Copyright © 2010 Pearson Education,
Inc.
chromosome (unduplicated)
in a daughter cell at interphase
Fig. 8.6, p. 131
Slide 4
What is DNA?
 DNA or deoxyribonucleic acid is a large
molecule made of chains of repeating units
called nucleotides.
 It contains the information for specifying the
proteins that allow life in other words it
contains instructions on how to make proteins
 Its structure was described for the first time in
1953 by James Watson and Francis Crick
(won the Nobel prize for it)
Copyright © 2010 Pearson Education, Inc.
5.2 Passing Genes and Chromosomes to
Daughter Cells
(a) DNA replication
 DNA molecule is split up the middle
of the helix (enzymes do this)
 Nucleotides are added to each side
(The enzyme is DNA polymerase)
 Result is two identical daughter
molecules, each with one parental
strand and one new strand. This is
called semiconservative replication
New strands
Parental strands
Copyright © 2010 Pearson Education, Inc.
Figure 5.5a
5.2 Passing Genes and Chromosomes to
Daughter Cells
 DNA polymerase:
the enzyme that
replicates DNA
 Forms covalent
bonds between
nucleotides on the
new strands
(b) The DNA polymerase enzyme facilitates replication.
Unwound DNA helix
DNA polymerase
DNA polymerase
Free nucleotides
Copyright © 2010 Pearson Education, Inc.
Figure 5.5b
5.2 Passing Genes and Chromosomes to
Daughter Cells
PLAY
Animation—The Structure of DNA
http://biologyinmotion.com/
Copyright © 2010 Pearson Education, Inc.
Assignment
 Study all of Ch 5 on Cancer, DNA synthesis,Mitosis, Meiosis &
The Cell Cycle. pp. 109-142.
Assignment: Hand in at the beginning of next class (typed) the
answers to questions 1-5 from the Savvy Reader (p.140).
Do the online assignment for Ch 5 www.masteringbiology.com
and submit to the grade tracker.
We’ll have a test on Chapter 5__Wed June 9_____
*Remember that your service learning hours will be due shortly
(room 1159)
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis
 Cell cycle: the “lifecycle” of the cell
 Three steps:
 Interphase: the DNA replicates
 Mitosis: the copied chromosomes are
moved into daughter cells (division of the
nucleus)
 Cytokinesis: the cell is split into 2 daughter
cells. (This is when the cytoplasm divides)
Copyright © 2010 Pearson Education, Inc.
What is the cell cycle?
 The cell cycle is an ordered set of events,
resulting in cell growth
and division into two daughter cells
 The stages of the cell cycle during
interphase are :
 G1 (stands for Gap1, growth takes place),
 S (stands for synthesis, this is when DNA is replicated)
G2 (stands for Gap 2)
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis - Interphase
 Three phases:
 G1: cell grows, organelles duplicate
 S: DNA replicates
 G2: cell makes proteins needed to complete
mitosis
 Most of the cell cycle is in interphase
Copyright © 2010 Pearson Education, Inc.
The Cell Cycle
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis - Mitosis
 Produces genetically-identical daughter
cells
 Sister chromatids are pulled apart
 Four stages: (PMAT)




Prophase
Metaphase
Anaphase
Telophase
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis - Mitosis
 Prophase:
 Nuclear envelope disappears
 Thin chromatids condense into shorter and
thick chromosomes
 Microtubules form a spindle (and pull the
chromosomes toward the middle of the cell)
 Animal cells: microtubules attached to
centrioles at the poles of the cell
 Metaphase: chromosomes are aligned
across the middle of the cell
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis - Mitosis
 Anaphase:
 centromeres split,
 sister chromatids are pulled apart toward opposite
poles by the microtubules in the spindle
 Telophase:
 Nuclear envelopes reform around chromosomes
 Chromosomes revert to uncondensed form
 Spindle dissapears
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis
Suggested Media Enhancement:
Mitosis
To access this animation go to folder
C_Animations_and_Video_Files and open the BioFlix folder.
Also look at mitosis tutorial in
www.cellsalive.com
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis - Cytokinesis
 Stage in which two daughter cells are
formed from the original one
 Plants:
 New cell wall forms between the cells, built
from cellulose
 Animals:
 Don’t have a cell wall
 Proteins pinch the original cell into two new
cells
 After cytokinesis, cells reenter interphase.
Copyright © 2010 Pearson Education, Inc.
5.3 The Cell Cycle and Mitosis
PLAY
Animation—Mitosis
PLAY
Animation—The Cell Cycle
Copyright © 2010 Pearson Education, Inc.
(4.5 min)
Control System of the Cell Cycle
 The distinct events of the cell cycle are directed by a
distinct cell cycle control system.
 These molecules trigger and coordinate key events in
the cell cycle.
 The control cycle has
a built-in clock, but it
is also regulated by
external adjustments
and internal controls.
Copyright
© 2002
PearsonInc.
Education,
Copyright
© 2010 Pearson
Education,
Inc., publishing as Benjamin Cummings
Cell cycle control system
 There are three major checkpoints in the cell
cycle. These are “stop and go” signals.(G1,
M, and G2)
 It checks whether or not the cellular
processes have been completed up to that
point so it can proceed.
 The G1 check point is very important. Nerve
cells and muscle cells switch into a non
dividing stage called G0. They do not get
a “go ahead” signal and stop dividing.
Copyright © 2010 Pearson Education, Inc.
5.4 Cell Cycle Control and Mutation
 G1 checkpoint: are growth factors
present?
 Cell must also be large enough and have
enough nutrients
 G2 checkpoint: has DNA replicated
properly?
 Metaphase checkpoint: have all
chromosomes attached properly to
microtubules?
Copyright © 2010 Pearson Education, Inc.
5.4 Cell Cycle Control and Mutation
 Proto-oncogenes: genes that code for the cell
cycle control proteins (control the cell cycle)
 Mutation: a change in the sequence of DNA
 This changes the structure and function of the
protein
 Mutations may be inherited or caused by
carcinogens
What is a proto-oncogene?
What is a mutation?
What are some examples of carcinogens?
Copyright © 2010 Pearson Education, Inc.
5.4 Cell Cycle Control and Mutation
 When proto-oncogenes mutate, they become
oncogenes
 Their proteins no longer properly regulate cell
division
 They usually overstimulate cell division
(a) Mutations to proto-oncogenes
Proto-oncogene
Mutation
Mutated proto-oncogene
(oncogene)
Mutation
DNA
Protein
Copyright © 2010 Pearson Education, Inc.
Functional protein
stimulates cell
division only when
conditions are right.
Mutated protein
may overstimulate
cell division by
overriding
checkpoint
control.
Figure 5.12a
5.4 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
(b) Mutations to tumor-suppressor genes
Tumor suppressor
Mutation
Mutated tumor
suppressor
Mutation
DNA
Protein
Copyright © 2010 Pearson Education, Inc.
Tumor-suppressor
protein stops tumor
formation by suppressing
cell division.
Mutated tumor
-suppressor
protein fails to stop
tumor growth.
Figure 5.12b
Some examples of genes involved in cancer
 P53- this is a tumor suppressor gene. It orders the cell
to self destruct if too damaged or tries to fix the damage. If p53
mutates and is not working damaged cells are allowed to
divide. 50% of cancers are due to a mutated p53 gene that
doesn’t work at the checkpoint.
 BRCA2 is a gene that makes a protein that repairs damaged
DNA. A mutant version cannot help repair DNA and it will allow
the cell to divide with the damage.
 Some Characteristics of Normal Cells
1. Normal cells exhibit contact inhibition
2.Normal cells exhibit anchorage dependency
3. Normal cells die after about 50 to 60 divisions
Copyright © 2010 Pearson Education, Inc.
5.4 Cell Cycle Control and Mutation - Many
Mutations Are Required for Cancer to
Develop
 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.
What is a telomere? telomerase? Enzyme that
prevents the degradation of the tips of chromosomes
Copyright © 2010 Pearson Education, Inc.
5.4 Cell Cycle Control and Mutation - Many
Mutations Are Required for Cancer to
Develop
 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
Copyright © 2010 Pearson Education, Inc.
5.5 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
Copyright © 2010 Pearson Education, Inc.
5.5 Cancer Detection and Treatment Treatment Methods
 Chemotherapy: drugs that selectively kill
dividing cells
 Combination of different drugs used
(“cocktail”). Cells become resistant to the
chemicals
 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)
Copyright © 2010 Pearson Education, Inc.
5.5 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
What is the meaning of “remission” when
talking about cancer?
Copyright © 2010 Pearson Education, Inc.
Reduction division to make sex cells or
gametes
Meiosis
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
What is 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
 Human somatic cells have 22 pairs of
autosomes, and one pair of sex
chromosomes
 Gametes are haploid;
 somatic cells are diploid
Copyright © 2010 Pearson Education, Inc.
What are homologous pairs of
chromosomes?
Humans have 46 chromosomes. 23 from the
mother and 23 from the father. We get a complete
set of genetic information from each parent.
 The chromosomes of these pairs that contain
similar genetic material and similar size and
shape are called homologous pairs of
chromosomes.
Copyright © 2010 Pearson Education, Inc.
 The chromosomes of a homologous pair
 Carry genes for the same characteristics
at the same place, or locus
Chromosomes
Centromere
Figure 8.12
Copyright © 2010 Pearson Education, Inc.
Sister chromatids
What is fertilization?
What is a zygote?
 Fertilization is the union of two gametes, one
from each parent.
A zygote is a fertilized egg. It is diploid.
 Each gamete is haploid. During fertilization the
diploid number is restored.
Ex: in humans the egg and the sperm each
contains 23 chromosomes so after fertilization the
fertilized egg will have 46 chromosomes
Copyright © 2010 Pearson Education, Inc.
Terms to know








Meiosis
Gametes
Diploid chromosome number
Haploid chromosome number
Zygote
Homologous chromosomes
Karyotype
Non-disjunction
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
Egg cell has 23
chromosomes
(unpaired).
Egg-producing
cells in the
ovary have 46
chromosomes
(23 pairs).
Meiosis
Sperm-producing
cells in the
testes have 46
chromosomes
(23 pairs).
Fertilization
Meiosis
Sperm cell has 23
chromosomes
(unpaired).
Diploid (2n)
Copyright © 2010 Pearson Education, Inc.
Haploid (n)
Zygote has 46
chromosomes
(23 homologous pairs).
Diploid (2n)
Figure 5.21
Meiosis: Two Divisions
 Two consecutive nuclear divisions
 Meiosis I
 Meiosis II
 DNA is NOT duplicated between divisions
 Four haploid nuclei are formed
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
 Before meiosis, there is an interphase –
DNA is duplicated
 Meiosis takes place in two stages:
meiosis I and meiosis II
End of previous
mitotic event
Cell growth and
preparation for
division
G2
Interphase
(G1, S, G2)
Copyright © 2010 Pearson Education, Inc.
Interphase and
Meiosis
S
G1
Cell growth
S and G phases
similar to the S and G
phases of mitosis
DNA is copied
Figure 5.22
5.6 Meiosis
 Meiosis I separates the members of a
homologous pair from each other.
 During prophase I there may be crossing
over between members of homologous pairs
 After meiosis I, the resulting cells are haploid
 Meiosis II is essentially like mitosis; it
separates the sister chromatids
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
4
Interphase and Meiosis
(G1, S1, G2)
2
Meiosis I
Meiosis II
Prophase I
Nuclear envelope starts to
break down. Microtubules start
to assemble. DNA condenses
into chromosomes.
Anaphase
Homologous
chromosomes are
separated by shortening
of microtubules.
4
Nuclear envelope
Replicated
uncondensed
DNA
Random alignments
2
Centrioles
Crossing
over may
occur.
1
3
Microtubules
Cell
membrane Nucleus
3
1
G2
G1
DNA is replicated
during S phase of
interphase.
Metaphase
Homologous
chromosomes align at
middle of cell.
S
Copyright © 2010 Pearson Education, Inc.
Figure 5.23
5.6 Meiosis
Interphase and Meiosis
(G1, S1, G2)
Meiosis I
6 Prophase II
Microtubules lengthen.
Meiosis II
8 Anaphase II
Sister chromatids are
separated by shortening of
microtubules.
8
6
5
7
9
5 Telophase I and
Cytokinesis Cytokinesis
results in two daughter cells.
Nuclear envelopes reform.
Copyright © 2010 Pearson Education, Inc.
7 Metaphase II
Chromosomes align
at middle of cell.
9 Telophase II and
Cytokinesis Four haploid
daughter cells result.
Nuclear envelopes reform.
Figure 5.23
5.6 Meiosis
 Crossing over: exchange of equivalent
portions of chromosomes between
members of a homologous pair
 Results in new types of gametes being
formed
Copyright © 2010 Pearson Education, Inc.
Mitosis
Meiosis
COMPARED
 Occurs in somatic
cells
 One duplication
one division
 Result in two
diploid (2N)
daughter cells
 Daughter cells are
identical to parent
cell
Copyright © 2010 Pearson Education, Inc.
 Occurs in gametes
only
 One duplication two
divisions
 Result in four haploid
(N) daughter cells
 Daughter cells are
different to parent cell.
Introduces variety.
5.6 Meiosis
(a) If crossing over does not occur in prophase I
Red flowers
Two types of gametes
White flowers
Meiosis
Long grains
Short grains
(b) If crossing over does occur in prophase I
Four types of gametes
Meiosis
Crossing over
Copyright © 2010 Pearson Education, Inc.
Figure 5.24
Crossing over
 Crossing over is the exchange of genetic
material (DNA) between homologous
chromosomes.
 During prophase I of meiosis, the
homologous portions of two non-sister
chromatids exchange places.
 They get so close to each other that
chromosomes form connections and
exchange sections of DNA
Copyright © 2010 Pearson Education, Inc.
Crossing Over
•Each chromosome
becomes zippered to its
homologue
•All four chromatids are
closely aligned
•Non-sister chromosomes
exchange segments
Copyright © 2010 Pearson Education, Inc.
Why is crossing over important?
 It produces VARIETY in the offspring
Check these meiosis tutorials:
 http://www.biology.arizona.edu/cell_bio/tut
orials/meiosis/page3.html
 http://www.biologymad.com
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
Suggested Media Enhancement:
Meiosis
To access this animation go to folder
C_Animations_and_Video_Files and open the BioFlix folder.
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
 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
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
(a) One possible metaphase I alignment
BRCA2 +
HER2 +
Two combinations of
chromosomes in gametes
BRCA2 +
HER2
+
BRCA2 +
HER2 +
1/2 normal gametes
Meiosis
BRCA2 –
HER2 –
BRCA2 –
HER2 –
1/2 gametes with two
mutant alleles
BRCA2 –
HER2 –
(b) Another possible metaphase I alignment
BRCA2 +
HER2 –
BRCA2 +
HER2 –
BRCA2 +
HER2 –
Two additional
combinations of
chromosomes in gametes
1/2 gametes with
HER2 mutation
Meiosis
BRCA2 –
HER2 +
BRCA2 –
Copyright © 2010 Pearson Education, Inc.
BRCA2 –
HER2 +
1/2 gametes with
BRCA2 mutation
HER2 +
Figure 5.25
5.6 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
Copyright © 2010 Pearson Education, Inc.
5.6 Meiosis
 For cancer mutations to be passed on to
offspring, they must take place in cells that
give rise to gametes.
 Mutations in somatic cells (e.g., skin
cancer) are not heritable.
Copyright © 2010 Pearson Education, Inc.
5.4 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
 What are proto-oncogenes?
 What are oncogenes?
Copyright © 2010 Pearson Education, Inc.
Karyotype and Alteration in
Chromosome Number
Copyright © 2010 Pearson Education, Inc.
ALTERATIONS OF CHROMOSOME
NUMBER AND STRUCTURE
What is a karyotype?
A karyotype is a photograph of an
individual’s chromosomes arranged in order
A karyotype is a picture, a display of the 46
chromosomes. Shows 23 pairs of
chromosomes, each pair with the same
length, centromere position, and staining
pattern.
Copyright © 2010 Pearson Education, Inc.
5,000
 Down syndrome is caused by trisomy 21
 An extra copy of chromosome 21
Figure 8.20A
Copyright © 2010 Pearson Education, Inc.
Figure 8.20B
 One aneuploid condition, Down syndrome, is due to
three copies of chromosome 21.
 It affects one in 700 children born in the United States.
 Although chromosome 21 is the smallest human
chromosome, it severely alters an individual’s phenotype.
Copyright © 2010 Pearson Education, Inc.
 The chance of having a Down syndrome
child
 Goes up with maternal age
Infants with Down syndrome
(per 1,000 births)
90
80
70
60
50
40
30
20
10
0
20
Figure 8.20C
Copyright © 2010 Pearson Education, Inc.
25
30
35
40
Age of mother
45
50
Sex chromosome pair
 Male pair is:
XY
 Female pair is: XX
How is sex determined?
Copyright © 2010 Pearson Education, Inc.
 Klinefelter’s syndrome, an XXY male, occurs
once in every 2000 live births.
 These individuals have male sex organs, but some are
sterile.
 There may be feminine characteristics, but their
intelligence is normal.
 Males with an extra Y chromosome (XYY) tend to
somewhat taller than average.
 Trisomy X (XXX), which occurs once in every
2000 live births, produces healthy females.
 Monosomy X or Turner’s syndrome (X0), which
occurs once in every 5000 births, produces
phenotypic, but immature females.
Copyright © 2010 Pearson Education, Inc.
Review Questions
1. What is mitosis? What are the functions of mitosis? What type of cells undergo mitosis?
2.What is a pathologist? An oncologist?
3. What is cancer? What is a tumor?
4. What is the difference between malignant and benign tumors?
5.What is a metastasis? How does it happen?
6. What is a carcinogen? Name 3 known carcinogens.
7. List 4 risk factors for cancer and explain why.
8. What is the difference between sexual reproduction and asexual reproduction?
9.What is DNA? Who described DNA structure and when? What is a chromosome? What is a
gene? What is our species number
10. What are sister chromatids? What is a centromere?
11. Describe what happens during DNA replication. Name an enzyme that facilitates DNA
replication.
12.What are the complementary bases? What type of chemical bond joins them? Why is this
bond advantageous in this case?
14. What is the cell cycle? What is included in interphase? What happens during the “S” part
of the cycle?
15. What are the stages of mitosis? What must happen before mitosis starts? What are the
most important things that happen in each?
16. Describe cytokinesis in animals. How is this different from cytokinesis is plants?
17. What are the “check points” in the cell cycle? What are some proteins that stimulate cells
to divide?
Copyright © 2010 Pearson Education, Inc.
Review questions (continued….)
18.What is the function of growth factor proteins?
19. What is a mutation? What causes mutations?
20. What are proto-oncogenes? When do they become oncogenes? What
do oncogenes do? Give an example of an oncogene.
21. What are tumor suppressors genes?
22. What is necessary for a malignant tumor to occur? What is the meaning
of “multiple hit model” of cancer development?
23. Describe what is “contact inhibition” and “anchorage dependence” and
explain what happens in cancerous cells.
24. How is cancer detected? What is a biopsy? A laparoscopy?
25. Describe the two common cancer treatments in use today.
26. What is meiosis? Where does it happen and what are the results of
meiosis?
27.Define the following: gonads, gametes, somatic cells, autosomes,
karyotype, zygote and homologous pairs of chromosomes.
28. What are alleles? What is the haploid number of chromososmes and
what is the diploid number of chromosomes?
Copyright © 2010 Pearson Education, Inc.
Review questions (continued….)
29.What must happen before meiosis? What is crossing over? When does it
happen?
30. What is the meaning of “random alignment”? When does it happen and
why is it important.
31. What happens when there are mistakes in meiosis? In mitosis? What is
non-disjunction?
32.What is the mane of a mistake that gives a person an extra
chromosome? Give two examples?
33. Be able to compare mitosis and meiosis in terms of the number of
daughter cells produced and chromosomes in the daughter cells.
34. What usually happens when there is an abnormal number of
chromosomes? Why are sex abnormalities more common?
Copyright © 2010 Pearson Education, Inc.
Review questions















1. What is cancer
2. What is a carcinogen? Give examples.
3. List five risk factors for cancer and explain why these increase the chances of getting
cancer.
4. What is the difference between a benign tumor and a malignant tumor? What is a
metastasis?
5. What are the main differences between normal cells and cancer cells?
6. What must happen before cell division can take place? What do parent cells must pass on to
daughter cells?
7. Where is DNA found? What is a chromosome? What is a gene?
8. What is DNA? Explain in general terms how DNA is replicated. Include the
complementary bases and why it is called “semi conservative replication”
9. What is the cell cycle? What are the stages of the cell cycle and what happens in each?
10. What are some factors known to control the cell cycle? What is the G0 stage and what
cells go into it?
11. What is mitosis. List the stages of mitosis in order and explain the main events that
happen during each one. What is cytokynesis?
12. What is the end result of mitosis? What is the result of mitosis?
13.What is the function of mitosis compared to the function of meiosis?
14. What is meiosis? What are homologous chromosomes? What is crossing over?
15.Discuss the main differences between mitosis and meiosis.
Copyright © 2010 Pearson Education, Inc.
More Review Questions
1. What is a somatic cell? An autosome?
2. Free radicals remove ______ from other molecules.
3.What is the name of a replicated chromosome? What is the name of the place where the two halves of
a duplicated chromosome are connected?
4.Which word describes a cancerous tumor?
5.List the events of the cell cycle in order.___,___,___,___,___. Which part of this is interphase?
6.If 25% of the bases of its DNA of one species are G. What percent would be C?
7.What are gametes? How many chromosomes gametes have compared to somatic cells? What is haploid?
Where do you find the Diploid chromosome number?
8.What are homologous chromosomes?
9.The gene that makes a protein that checks for mistakes at a checkpoint in the life cycle of a cell is _______
gene.
10.A gene that controls the cell cycle of a cell is called a/an _______ gene.
11.What is likely to happen if the p53 gene is damaged is mutated?
12.What is the meaning of the “multiple hit” model of cancer?
13.What is a biopsy?
14.What is the result of radiation therapy?
15.What is chemotherapy?
16. What is CA125 test? Why is it not practical to do routine tests for CA125?
17. What is the name of the process by which tumors attract blood vessels to create their own blood supply?
18. What is the name given to genes that are in the same chromosome?
19. During which part of meiosis crossing over occurs? Why is crossing over important?
20. List two types of inhibitions that are lost in cancer cells.
Copyright © 2010 Pearson Education, Inc.