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Slide 1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
CHAPTER 8 – CELLULAR REPRODUCTION: CELLS
FROM CELLS
Slide 2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
State StandardsStandard 2:
Standard 5a:
Standard 5b:
Slide 3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
State StandardsStandard 2a:
Standard 2b:
Slide 4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The life cycle of a multicellular organism includes
• This sea star embryo (morula) shows one stage in the development of a fertilized egg
– The cluster of cells will continue to divide as development proceeds
Slide 5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Introduction to Cell Division
Life cycle – the sequence of life stages leading from the adults of one generation to the adults of the next
• Development phase –
• Reproduction phase – formation of new individuals from preexisting ones
Slide 6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cell division is at the heart of the reproduction of cells and organisms
• Organisms can reproduce sexually or asexually
CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION
Slide 7
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
In asexual reproduction, single-celled organisms reproduce by simple cell division.
Slide 8
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Some multicellular organisms can divide into pieces that then grow into new individuals.
– This sea star is regenerating a lost arm
– Regeneration
Slide 9
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Some organisms make exact copies of themselves, asexual reproduction
Like begets like, more or less
Figure 8.1A
Slide 10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Other organisms make similar copies of themselves in a more complex process, sexual reproduction
Figure 8.1B
Slide 11
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Introduction of Cell Division
• Sexual reproduction –
• Asexual reproduction – production of offspring by a single parent
Slide 12
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Comparing Asexual and Sexual Reproduciton
• See What Cell Reproduction Accomplishes reading notes
Slide 13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• All cells come from cells
• Cell division –
• Main roles:
– The development of a fertilized egg to an adult, how organisms grow to adult size
– Asexual reproduction or the formation of eggs and sperm
Cells arise only from preexisting cells
Slide 14
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Prokaryotic cells divide asexually
– These cells possess a single chromosome, containing genes
– The chromosome is replicated
– The cell then divides into two cells, a process called
Prokaryotes reproduce by binary fission
Figure 8.3B
Prokaryotic chromosomes
Slide 15
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.3A
• Binary fission of a prokaryotic cell
Prokaryoticchromosome
Plasmamembrane
Cell wallDuplication of chromosomeand separation of copies
Continued growth of the cell and movement of copies
Division intotwo cells
Slide 16
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– Almost all of the genes of a eukaryotic cell are located on chromosomes in the cell nucleus.
• Chromosome – DNA containing structure found in the nucleus of an eukaryotic cell. It carries the organism’s genetic information
• Gene – a unit of hereditary information consisting of a specific nucleotide sequence of DNA
Chromosomes
Slide 17
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Eukaryotic Chromosomes
– Each eukaryotic chromosome contains
• Proteins – help organize the DNA and control the activity of the genes
– The number of chromosomes in a eukaryotic cell depends on the species.
Slide 18
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.3
Slide 19
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Chromosomes
• Chromosomes can exist as
– Chromatin –
– Compact, distinct structures that are visible under the light microscope. Occur when the cell is dividing.
Slide 20
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.4
Slide 21
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Before a cell starts dividing, the chromosomes are duplicated– This process
produces sister chromatids –
– Centromere –
Centromere
Sister chromatids
Figure 8.4B
Slide 22
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• When the cell divides, the sister chromatids separate
– Two daughter cells are produced
– Each has a complete and identical set of chromosomes
Centromere Sister chromatids
Figure 8.4C
Chromosomeduplication
Chromosomedistribution
todaughter
cells
Slide 23
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cell Cycle
Cell cycle – orderly sequence of events that occur from the formation of a new cell by division to that cell dividing.
Slide 24
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The cell cycle consists of two major phases:
– Interphase, where chromosomes duplicate and cell parts are made
– The mitotic phase, when cell division occurs
The cell cycle multiplies cells
Figure 8.5
Slide 25
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cell CycleThe cell cycle can be divided into:
1. Interphase
a. G1 phase – the cell increases in size,
the number of organelles and proteins
increase
b. S phase –
c. G2 phase – period of rapid growth, cell
prepares to divide by producing the
proteins needed for cell division.
Slide 26
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 27
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 28
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA ReplicationDNA Replication
Origins of replication – the specific sites on the DNA where DNA replication begins.
– Enzymes (DNA helicase) attach to the origins of replication and break the hydrogen bonds between the bases
– Causes the 2 DNA strands to separate
– Creates a replication bubble
Slide 29
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA Replication
• The separated strands act as a template to create the new complementary strands
– New nucleotides are added to the bases of each parent strand
– DNA polymerase adds the new DNA nucleotides
• Only adds nucleotides to the 3’ end of the growing strand
• The new strand only grows from
Slide 30
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA Replication
• One strand is synthesized in one continuous piece – leading strand
• Other strand is synthesized in pieces (Okazaki fragments) – lagging strand
• DNA ligase joins the pieces in the lagging strand
Slide 31
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA Replication
• Once daughter strands are completed DNA polymerase checks for any errors and corrects them (proofreads)
Slide 32
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
DNA Replication
Result of DNA Replication
• 2 DNA molecules are formed that are exactly alike
• Each DNA molecule contains
– 1 nucleotide chain from the original DNA
– 1 new nucleotide chain formed during replication
– This makes DNA replication
Slide 33
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Quickwrite
• Describe the process of DNA replication. Include the following terms in your description.
DNA polymerase Okazaki fragments
Origin of replication ligase
helicase
Leading strand semiconservative replication
Lagging strand
Slide 34
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cells continue dividing until they touch one another
– This is called
Cells anchor to dish surface and divide.
Figure 8.8A
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).
Slide 35
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most animal cells divide only when stimulated, and others not at all
• In laboratory cultures, most normal cells divide only when attached to a surface
– They are
Anchorage, cell density, and chemical growth factors affect cell division
Slide 36
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Growth factors are
• Density dependent inhibition may be due to an inadequate supply of growth factor
After forming a single layer, cells have stopped dividing.
Figure 8.8B
Providing an additional supply of growth factors stimulates further cell division.
Slide 37
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Growth factors within the cell control the cell cycle
– Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide
Growth factors signal the cell cycle control system
G1 checkpoint
M checkpoint G2 checkpoint
Controlsystem
Figure 8.9A
Slide 38
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Growth factors control the cell cycle at 3 key checkpoints
1. In the G1 phase – for many cells this is the most important
2. In the G2 phase
3. In the M (metaphase) phase
Slide 39
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cancer cells have abnormal cell cycles
– They divide excessively and can form abnormal masses called tumors
– Are unrestrained by the systems that normally control cell division
• Don’t need growth factors to move past checkpoints
• Synthesize own growth factors
Growing out of control, cancer
Slide 40
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.18
Slide 41
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.19
Slide 42
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.20b
Slide 43
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
CancerTumor – an abnormal mass of cells due to
excessive growth
- benign
stay at original site
don’t usually impair normal function
can be completely removed by surgery
Slide 44
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cancer
malignant
– mass of cancer cells
- can impair normal function of tissue,
organ
Slide 45
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.20a
Slide 46
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Malignant tumors can invade other tissues and may kill the organism
Tumor
Figure 8.10
Glandulartissue
1 2 3A tumor grows from a single cancer cell.
Cancer cells invade neighboring tissue.
Lymphvessels
Cancer cells spread through lymph and blood vessels to other parts of the body.
Metastasis
Slide 47
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 11.1
Slide 48
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cancer
Cancer Treatment
Radiation – expose cancerous tumors to high energy radiation which disrupts cell division
Chemotherapy – drugs are administered that disrupt cell division
Slide 49
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cancer Prevention
• Self Examination
– Breast
– Testicular
– Skin
• Healthy Lifestyle
– Sunblock
– Avoid tobacco, drugs
– Balanced diet
– Exercise
• Medical Tests
– Pap smear
– Colonoscopy
Slide 50
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cell Cycle2. Mitotic Phase – two daughter cells are produced that
are identical to one another.
a. Mitosis
-
- the duplicated chromosomes are
separated and evenly distrubuted to form
2 daughter nuclei
Slide 51
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cell Cycle
Interphase
• Chromosomes not visible – in the form of chromatin
• Nucleus visible
• Nucleus contains 1 or more nucleoli
• Centrosomes have duplicated
Slide 52
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stages of Mitosis
Prophase
• Nuclear envelope breaks into fragments
• Nucleoli disappear
• Mitotic spindle begins to form
• Chromosomes coil and are visible
Slide 53
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stages of Mitosis
Metaphase
• Mitotic spindle is fully formed
• Chromosomes are lined up along the metaphase plate
Slide 54
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stages of Mitosis
Anaphase
• Sister chromatids separate
• Kinetochore fibers move the separated chromatids to opposite sides of the cell
• Non-kinetochore fibers elongate the cell
Slide 55
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Stages of Mitosis
Telophase
• Daughter nuclei appear as nuclear envelope forms around separated chromosomes
• Nucleoli form in each nucleus
• Mitotic spindle breaks down
• Chromosomes uncoil to form chromatin
Slide 56
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Write the name of the stage of cell cycle being described
1. The chromosomes are lined up in the middle of the cell
2. The 2 groups of chromosomes have reached the cell poles
3. Period of cell growth
4. Mitotic spindle is fully formed
5. Sister chromatids of each chromosome separate
6. The nuclear envelope breaks up
7. The chromosomes are duplicated
8. Daughter chromosomes are “walked” by motor proteins toward opposite poles
9. Chromosomes uncoil
10. Each chromosome appears
Slide 57
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cell Cycle
b. Cytokinesis – the division of the cytoplasm
Slide 58
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• In animals, cytokinesis occurs by cleavage
– This process pinches the cell apart
Cytokinesis differs for plant and animal cells
Figure 8.7A
Cleavagefurrow
Cleavagefurrow
Contracting ring ofmicrofilaments
Daughter cells
Slide 59
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• In plants, a membranous cell plate splits the cell in two
Vesicles containingcell wall material
Cell plateforing
Figure 8.7BCell plate Daughter
cells
Wall ofparent cell
Daughternucleus
New cell wall
Slide 60
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Somatic cells of each species contain a specific number of chromosomes
– Human cells have 46, making up 23 pairs of homologous chromosomes
MEIOSIS AND CROSSING OVER
Chromosomes are matched in homologous pairs
Chromosomes
Centromere
Sister chromatids Figure 8.12
Slide 61
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Homologous Chromosomes
• Humans have 23 pairs of homologous chromosomes
– 22 pairs – autosomes –
– 1 pair – sex chromosomes,
XX = female,
XY= male
Slide 62
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Homologous Chromosomes• Matched pairs of chromosomes
• Similar in
• Both carry genes controlling the same inherited characteristics (the version of the gene may be different)
• The genes are located
• One chromosome of each pair is inherited from the mother, the other from the father
Slide 63
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The human life cycle
Figure 8.13
MEIOSIS FERTILIZATION
Haploid gametes (n = 23)
Egg cell
Sperm cell
Diploidzygote
(2n = 46)Multicellular
diploid adults(2n = 46)
Mitosis anddevelopment
Slide 64
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Human Life Cycle
Diploid cells (2n) – cells that contain both homologous chromosomes. In humans
Haploid cells (n) – cells with one copy of each homologous chromosome. The gametes (egg and sperm) are haploid. In humans
Slide 65
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Meiosis
Meiosis
• In animals, meiosis results in the formation of haploid egg and sperm cells.
Slide 66
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.15
Slide 67
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.16.2
Slide 68
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
MeiosisTwo nuclear divisions occur:
1. Meiosis I
a. During prophase I homologous chromosomes pair –
b. During prophase I the paired chromosomes exchange chromosome parts –
c. Homologous chromosomes are separated
d. 2 cells produced each containing one copy of each homologous chromosome
Slide 69
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Model of Meiosis Conclusion
Meiosis I – Explain what happens during each of the stages of meiosis one and what is produced at the end of meiosis I. In your explanation include the following:
DNA Replication Interphase
Homologous chromosomes Prophase I
Synapsis Metaphase I
Crossing over Anaphase I
Telophase I
Slide 70
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.16.3
Slide 71
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Meiosis
2. Meiosis II
a. Not preceded by the replication of DNA
b. Sister chromatids of each chromosome are separated
c. Produces
Slide 72
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Model of meiosis conclusion
• Describe what occurs during each phase of meiosis II and what is formed at the end of this phase.
Slide 73
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Meiosis
Meiosis produces 4 cells that
• Are haploid
• Chromosome makeup of each is
Slide 74
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.17
Slide 75
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Comparing Mitosis and MeiosisMitosis
1.
2.
3. Involves one cell division
4.
5. Individual chromosomes line up at the metaphase plate
Meiosis
1. Produces haploid cells
2. Cells produced are unlike the parent
3.
4. Homologous chromosomes pair and then separate
5.
Slide 76
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Comparing Mitosis and Meiosis
Mitosis
6. No crossing over occurs
7.
Meiosis
6.
7. Needed for sexual reproduction
Slide 77
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 78
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Meiosis
Spermatogenesis
• Formation of sperm by meiosis
• Occurs in special cells (spermatogonia) in the testes
Slide 79
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 80
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Meiosis
Oogenesis
• Formation of an egg by meiosis
• Occurs in special cells (oogonia) in the ovaries
• Unequal divisions of the cytoplasm during meiosis I and meiosis II result in the formation of 1 haploid egg and 3 haploid polar bodies
Slide 81
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 82
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Identify if statement is describing oogenesis, spermatogenesis or both.
1. Occurs in the testes.
2. Produces 4 haploid cells.
3. Only one cell can take part in fertilization.
4. A continuous process.
5. Begins before birth.
Slide 83
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Genetic Recombination
• Genetic Recombination –
• There are 4 processes that contribute to genetic recombination.
Slide 84
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.18
Slide 85
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Independent Assortment of Chromosomes
• The large number of possible arrangements of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes
– This results in 2n possible combinations of gametes
– For humans 2n = 223 = 8 million possible combinations
Slide 86
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.17A, B
Coat-color genes Eye-color genes
Brown Black
C E
c e
White Pink
C E
c e
C E
c e
Tetrad in parent cell(homologous pair of
duplicated chromosomes)
Chromosomes ofthe four gametes
Slide 87
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The differences between homologous chromosomes are based on the fact that they can carry different versions of a gene at corresponding loci
Homologous chromosomes carry different versions of genes
Slide 88
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.18A
TetradChaisma
Centromere
Slide 89
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.19
Slide 90
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Genetic Recombination
Crossing over
• The exchange of genetic information between 2 homologous chromosomes.
Random fertilization
• Depends on which sperm cell and its chromosome combinations fertilizes which egg
Slide 91
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Identify the process that contributes to genetic recombination
1. Occurs during prophase I
2. Occurs during metaphase I
3. The reason homologous chromosomes can be different from one another.
4. The possible arrangements of the homologous chromosomes when lining up along the equator.
5. Depends on which sperm cell fertilizes which egg.
6. The exchange of info between homologous chromosomes
7. Results in 2n possible combinations of gametes
Slide 92
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Preparation of a karyotype
Figure 8.19
Blood culture
1
Centrifuge
Packed redAnd white blood cells
Fluid
2
Hypotonic solution
3
Fixative
WhiteBloodcells
Stain
4 5
Centromere
Sisterchromatids
Pair of homologouschromosomes
Slide 93
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• To study human chromosomes microscopically, researchers stain and display them as a karyotype
– A karyotype usually shows
ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE
A karyotype is a photographic inventory of an individual’s chromosomes
Slide 94
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Abnormal chromosome count is a result of nondisjunction
– Either homologous pairs fail to separate during meiosis I
8.21 Accidents during meiosis can alter chromosome number
Figure 8.21A
Nondisjunctionin meiosis I
Normalmeiosis II
Gametes
n + 1 n + 1 n – 1 n – 1Number of chromosomes
Slide 95
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– Or sister chromatids fail to separate during meiosis II
Figure 8.21B
Normalmeiosis I
Nondisjunctionin meiosis II
Gametes
n + 1 n – 1 n nNumber of chromosomes
Slide 96
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Fertilization after nondisjunction in the mother results in a zygote with an extra chromosome
Figure 8.21C
Eggcell
Spermcell
n + 1
n (normal)
Zygote2n + 1
Slide 97
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• This karyotype shows three number 21 chromosomes
• An extra copy of chromosome 21 causes Down syndrome
Connection: An extra copy of chromosome 21 causes Down syndrome
Figure 8.20A, B
Slide 98
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.23
The chance of having a Down syndrome child goes up with maternal age
Slide 99
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Alterations of Chromosomes
• In most cases abnormal chromosome number results in spontaneous abortion long before birth.
• Nondisjunction in the sex chromosomes has less of an affect on survival
Slide 100
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• Nondisjunction can also produce
• Unusual numbers of sex chromosomes upset the genetic balance less than an unusual number of autosomes
Connection: Abnormal numbers of sex chromosomes do not usually affect survival
Slide 101
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 8.1
Slide 102
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Slide 103
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer
– Four types of rearrangement are deletion, duplication, inversion, and translocation
Connection: Alterations of chromosome structure can cause birth defects and cancer
Slide 104
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Figure 8.23A, B
Deletion
Duplication
Inversion
Homologouschromosomes
Reciprocaltranslocation
Nonhomologouschromosomes
Slide 105
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Alterations of Chromosomes
Abnormalities in the structure of the chromosome may cause disorders (Figure 8.23A)
1. Deletion – a chromosome breaks and a fragment is lost.
2. Duplication – the fragment joins to a homologous chromosome.
Slide 106
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Alterations of Chromosomes
3. Inversion – the fragment reattaches to the original chromosome but in reverse orientation.
4. Translocation (Figure 8.23B) – attachment of a chromosome fragment to a nonhomologous chromosome. May/may not be harmful.
Slide 107
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Chromosomal changes in a somatic cell can cause cancer
Figure 8.23C
Chromosome 9
– A chromosomal translocation in the bone marrow is associated with chronic myelogenous leukemia
Chromosome 22Reciprocaltranslocation
“Philadelphia chromosome”
Activated cancer-causing gene