copyright © 2010 pearson education, inc. figure 5.2 chapter 5 cancer dna synthesis, mitosis, and...
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Copyright © 2010 Pearson Education, Inc. Figure 5.2
Chapter 5
Cancer DNA Synthesis, Mitosis, and Meiosis
Copyright © 2010 Pearson Education, Inc.
5.1
Figure 5.2
Chapter 5 Section 1
What Is Cancer?
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5.1 What Is Cancer?
What Is Cancer? Unregulated cell division Tumor: mass of cells with no function
Figure 5.2
Benignif tumor has noeffect onsurrounding tissue(noncancerous)
Metastaticif individual cells breakaway and start a newtumor elsewhere(cancerous)
Malignantif tumor invadessurrounding tissue(cancerous)
Normal cell division Unregulated cell division
Tumor
Potentiallycancerous
cell
Normalcell
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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
Figure 5.2
Benignif tumor has noeffect onsurrounding tissue(noncancerous)
Metastaticif individual cells breakaway and start a newtumor elsewhere(cancerous)
Malignantif tumor invadessurrounding tissue(cancerous)
Normal cell division Unregulated cell division
Tumor
Potentiallycancerous
cell
Normalcell
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5.1 What Is Cancer?
Metastatic cells 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.
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5.1 What Is Cancer?
Cancer cells differ from normal cells:1. Divide when they shouldn’t
2. Invade surrounding tissues
3. Move to other locations in the body
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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
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5.1 What Is Cancer? - Risk factors
Risk factors continuedLack 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 from carcinogens
Cells that divide frequently
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5.1
Figure 5.2
End of Chapter 5 Section 1
What Is Cancer?
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5.2
Figure 5.2
Chapter 5 Section 2
Passing Genes and Chromosomes to Daughter Cells
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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
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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).
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5.2 Passing Genes and Chromosomes to Daughter Cells
Chromosomes are uncondensed before cell division
They are duplicated through DNA replication Duplicated chromosomes, held together at the
centromere, are called sister chromatids
Figure 5.6
Unduplicatedchromosome
Duplicatedchromosome
A
b
C
A
b
C C
Sisterchromatids
Centromere
b
A
Replication
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5.2 Passing Genes and Chromosomes to Daughter Cells
DNA Replication DNA molecule is split up the
middle of the helix Nucleotides are added to each
side Result is two identical daughter
molecules, each with one parental strand and one new strand (semiconservative replication)
Figure 5.5a
(a) DNA replication
New strands
Parental strands
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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
Forms hydrogen bond between nitrogenous bases
Figure 5.5b
(b) The DNA polymerase enzyme facilitates replication.
Unwound DNA helix
Free nucleotides
DNA polymerase
DNA polymerase
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5.2 Passing Genes and Chromosomes to Daughter Cells
Animation—The Structure of DNAPLAY
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5.2
Figure 5.2
End of Chapter 5 Section 2
Passing Genes and Chromosomes to Daughter Cells
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5.3
Figure 5.2
Chapter 5 Section 3
The Cell Cycle and Mitosis
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5.3 The Cell Cycle and Mitosis
Cell cycle: the “lifecycle” of the cell Three steps:
1. Interphase: the DNA replicates
2. Mitosis: the copied chromosomes are moved into daughter cells
3. Cytokinesis: the cell is split into 2 daughter cells
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5.3 The Cell Cycle and Mitosis - Interphase
Interphase has three phases:1. G1: cell grows, organelles duplicate
2. S: DNA replicates
3. G2: cell makes proteins needed to complete mitosis
Most of the cell cycle
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5.3 The Cell Cycle and Mitosis - Mitosis
Mitosis Produces genetically-identical daughter
cells Sister chromatids are pulled apart Four stages:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
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5.3 The Cell Cycle and Mitosis - Mitosis Prophase: cell prepares for division
Replicated chromosomes condense Nuclear envelope disappears Microtubules pull the chromosomes toward
the middle of the cell In Animal cells, microtubules are attached
to centrosomes at the poles of the cell
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5.3 The Cell Cycle and Mitosis - Mitosis
Metaphase: chromosomes prepare for separation chromosomes are aligned across the middle
of the cell
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5.3 The Cell Cycle and Mitosis - Mitosis
Anaphase: chromotids separate centromeres split, sister chromatids are pulled apart toward
opposite poles
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5.3 The Cell Cycle and Mitosis - Mitosis
Telophase: cells finalize nuclear division Nuclear envelopes reform around
chromosomes Chromosomes revert to uncondensed form
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5.3 The Cell Cycle and Mitosis
Animation—MitosisPLAY
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5.3 The Cell Cycle and Mitosis - Cytokinesis
Cytokinesis Stage in which two daughter cells are
formed from the original one In Plants, a new cell wall forms between the
cells, built from cellulose
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5.3 The Cell Cycle and Mitosis - Cytokinesis
Cytokinesis Animals:
Don’t have a cell wall Proteins pinch the original cell into two new
cells
After cytokinesis, cells reenter interphase.
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5.3 The Cell Cycle and Mitosis
Mitosis
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5.3
Figure 5.2
End of Chapter 5 Section 3
The Cell Cycle and Mitosis
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5.4
Figure 5.2
Chapter 5 Section 4
Cell Cycle Control and Mutation
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5.4 Cell Cycle Control and Mutation
Control of the Cell Cycle 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
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5.4 Cell Cycle Control and Mutation
3 checkpoints during the cell cycle
1.G1 checkpoint: are growth factors present? Cell must also be large enough and have
enough nutrients
2.G2 checkpoint: has DNA replicated properly?
3.Metaphase checkpoint: have all chromosomes attached properly to microtubules?
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5.4 Cell Cycle Control
Animation—The Cell CyclePLAY
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5.4 Cell Cycle Control and Mutation
Cell Cycle Control and Cancer
Two important genes
1.Proto-oncogenes
2.Tumor-suppressor genes
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5.4 Cell Cycle Control and Mutation
Proto-oncogenesProto-oncogenes are genes that code for the cell cycle control proteins
Many proto-oncogenes encode for growth factors
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
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5.4 Cell Cycle Control and Mutation
OncogenesWhen proto-oncogenes mutate, they become oncogenes
Their proteins no longer properly regulate cell division
They usually over stimulate cell division
Figure 5.12a
(a) Mutations to proto-oncogenes
Functional proteinstimulates celldivision only whenconditions are right.
Mutated proteinmay overstimulatecell division byoverridingcheckpointcontrol.
Mutation Mutation
Protein
DNA
Proto-oncogeneMutated proto-oncogene(oncogene)
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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
Figure 5.12b
(b) Mutations to tumor-suppressor genes
Tumor-suppressorprotein stops tumorformation by suppressingcell division.
Mutated tumor-suppressorprotein fails to stop tumor growth.
Mutation
Protein
MutationDNA
Tumor suppressorMutated tumorsuppressor
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5.4 Cell Cycle Control and Mutation –
Many Mutations Are Required for Cancer to Develop
Angiogenesis: tumor gets its own blood supply Loss of contact inhibition: cells will now pile up
on each other
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5.4 Cell Cycle Control and Mutation –
Many Mutations Are Required for Cancer to Develop
Loss of anchorage dependence: enables a cancer cell to move to another location
Immortalized: cells no longer have a fixed number of cell divisions
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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
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5.4
Figure 5.2
End of Chapter 5 Section 4
Cell Cycle Control and Mutation
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5.5
Figure 5.2
Chapter 5 Section 5
Cancer Detection and Treatment
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5.5 Cancer Detection and Treatment
Cancer Detection Early detection and treatment is best
Different detection methods for different cancers1. Some cancers produce increased amount
of a characteristic protein2. Biopsies
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5.5 Cancer Detection and Treatment
Biopsy: surgical removal of cells or fluid for analysis Needle biopsy: removal is made using a
needle Laparoscope: surgical instrument with a
light, camera, and small scalpel
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5.5 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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5.5 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
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5.5
Figure 5.2
End of Chapter 5 Section 5
Cancer Detection and Treatment
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5.6
Figure 5.2
Chapter 5 Section 6
Meiosis – cell division for reproduction
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5.6 MeiosisChromosomes of Somatic Cells Humans have 46 chromosomes Chromosomes come in homologous pairs
Diploid – cells have a pair of each chromosome 22 pairs of autosomes 1 pair of sex chromosomes
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5.6 Meiosis
Homologous pairs of chromosomes carry the same genes.
Alleles But each chromosomes may carry a different
version of the gene, called alleles Alleles code for a different version of the same protein
Figure 5.22
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5.6 MeiosisMeiosis Specialized form of cell division in gonads to
produce gametes Meiosis reduces number of chromosomes in
each cell by one-half Gamete gets one of each pair Somatic cells are diploid (2n), but gametes are
haploid (1n)
•Eggs and sperm fuse to form diploid Zygote
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5.6 Meiosis
Chromosome Replicaton Before meiosis can occur, DNA is duplicated DNA is duplicated in the S phase Creates 2 sister chromotids
Held together by centromere
Figure 5.22
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5.6 Meiosis
MeiosisCell division that reduces diploid to haploid Meiosis takes place in two stages:
meiosis I and meiosis II
Figure 5.22
G1
S
Cell growth andpreparation fordivision
End of previousmitotic event
S and G phasessimilar to the S and Gphases of mitosis
Interphase andMeiosis Cell growth
Interphase(G1, S, G2) DNA is copied
G2
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5.6 Meiosis
Steps of Meiosis Meiosis I separates the members of a
homologous pair from each other. After meiosis I, the resulting cells are haploid (n) Meiosis I is therefore called ‘reduction division’
Meiosis II is essentially like mitosis; it separates the sister chromatids
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5.6 Meiosis
Four Steps of Meiosis I Meiosis I separates the members of a
homologous pair from each other.1. During prophase I there may be crossing
over between members of homologous pairs
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5.6 Meiosis
Four Steps of Meiosis I
2.Metaphase I homologous pairs line up at the equator of cell Microtubules attach to centromere
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5.6 Meiosis
Four Steps of Meiosis I
3.Anaphase I Homologous pairs are separated by shortening
microtubules
4.Telophase I – nuclear envelop reforms
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5.6 Meiosis
Meiosis II Consists of Prophase II, Metaphase II,
Anaphase II, and Telophase II Virtually identical to mitosis Sister chromatids are separated
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5.6 Meiosis
Two events create millions of different gametes from each parent1. Crossing over during prophase I
2. Random alignment during metaphase I
> Both increase the variation of next generation
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5.6 Meiosis
1. Crossing over during prophase I exchange of equivalent portions of
chromosomes between members of a homologous pair
Results in new assortment of genes in gametes
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5.6 Meiosis
1. Random Assortment during metaphase I Homologous pairs of chromosomes arrange
arbitrarily at cell equator
Results in new assortment of genes in gametes
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5.6 Meiosis
Meiosis
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5.6 Meiosis - Mistakes in 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)
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5.6 Meiosis - Mistakes in Meiosis
Human Nondisjunction of autosomes
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5.6 Meiosis - Mistakes in Meiosis
Human Nondisjunction of sex chromosomes
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5.6 Meiosis
Inheriting Cancer For cancer mutations to be passed on to
offspring, they must occur in cells that give rise to gametes.
Mutations in somatic cells (e.g., skin cancer) are not heritable.
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Comparison of Mitosis & Meiosis – Fig 5.27
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5.6
Figure 5.2
End of Chapter 5 Section 6
Meiosis – cell division for reproduction
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5.6
Figure 5.2
End of Chapter 5