Chapter 8 The Cellular Basis of Reproduction and Inheritance...– Asexual reproduction –...
Transcript of Chapter 8 The Cellular Basis of Reproduction and Inheritance...– Asexual reproduction –...
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Copyright © 2009 Pearson Education, Inc.
PowerPoint Lectures for
Biology: Concepts & Connections, Sixth Edition
Campbell, Reece, Taylor, Simon, and Dickey
Chapter 8 The Cellular Basis of
Reproduction and Inheritance
Lecture by Mary C. Colavito
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Saving an endangered plant
– The bellflower is an endangered species in Hawaii
– When the last plant was flowering, rescuers bought pollen for sexual reproduction
– Unfortunately, no offspring were produced
– Asexual reproduction is now being attempted
Introduction: Rain Forest Rescue
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CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION
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8.1 Like begets like, more or less
Living organisms reproduce by two methods
– Asexual reproduction
– Offspring are identical to the original cell or organism
– Involves inheritance of all genes from one parent
– Sexual reproduction
– Offspring are similar to parents, but show variations in traits
– Involves inheritance of unique sets of genes from two parents
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Cell division perpetuates life
– Cell division is the reproduction of cells
– Virchow’s principle states ―Every cell from a cell‖
8.2 Cells arise only from preexisting cells
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– Roles of cell division
– Asexual reproduction
– Reproduction of an entire single-celled organism
– Growth of a multicellular organism
– Growth from a fertilized egg into an adult
– Repair and replacement of cells in an adult
– Sexual reproduction
– Sperm and egg production
8.2 Cells arise only from preexisting cells
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Binary fission means ―dividing in half‖
– Occurs in prokaryotic cells
– Two identical cells arise from one cell
– Steps in the process
– A single circular chromosome duplicates, and the copies begin to separate from each other
– The cell elongates, and the chromosomal copies separate further
– The plasma membrane grows inward at the midpoint to divide the cells
8.3 Prokaryotes reproduce by binary fission
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Prokaryoticchromosome
Duplication of chromosomeand separation of copies
Cell wall
Plasmamembrane
1
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Prokaryoticchromosome
Duplication of chromosomeand separation of copies
Cell wall
Plasmamembrane
1
Continued elongation of thecell and movement of copies
2
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Prokaryoticchromosome
Duplication of chromosomeand separation of copies
Cell wall
Plasmamembrane
1
Continued elongation of thecell and movement of copies
2
Division intotwo daughter cells
3
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Prokaryotic chromosomes
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THE EUKARYOTIC CELL CYCLE AND MITOSIS
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Eukaryotic chromosomes are composed of chromatin
– Chromatin = DNA + proteins
– To prepare for division, the chromatin becomes highly compact, and the chromosomes are visible with a microscope
– Early in the division process, chromosomes duplicate
– Each chromosome appears as two sister chromatids, containing identical DNA molecules
– Sister chromatids are joined at the centromere, a narrow region
8.4 The large, complex chromosomes of eukaryotes duplicate with each cell division
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Sister chromatids
Centromere
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Centromere
Chromosomeduplication
Sister chromatids
Chromosomedistribution
todaughter
cells
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The cell cycle is an ordered sequence of events for cell division
It consists of two stages
– Interphase: duplication of cell contents
– G1—growth, increase in cytoplasm
– S—duplication of chromosomes
– G2—growth, preparation for division
– Mitotic phase: division
– Mitosis—division of the nucleus
– Cytokinesis—division of cytoplasm
8.5 The cell cycle multiplies cells
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S
(DNA synthesis)G1
G2
INTERPHASE
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Mitosis progresses through a series of stages
– Prophase
– Prometaphase
– Metaphase
– Anaphase
– Telophase
Cytokinesis often overlaps telophase
8.6 Cell division is a continuum of dynamic changes
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A mitotic spindle is required to divide the chromosomes
– The mitotic spindle is composed of microtubules
– It is produced by centrosomes, structures in the cytoplasm that
– Organize microtubule arrangement
– Contain a pair of centrioles in animal cells
– The role of centrioles in cell division is unclear
8.6 Cell division is a continuum of dynamic changes
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Video: Animal Mitosis
Video: Sea Urchin (time lapse)
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Centrosomes(with centriole pairs) Kinetochore
Early mitoticspindle
Chromatin
INTERPHASE PROMETAPHASEPROPHASE
Centrosome Fragmentsof nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Nuclearenvelope
Spindlemicrotubules
Nucleolus
Centromere
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Centrosomes(with centriole pairs) Kinetochore
Early mitoticspindle
Chromatin
INTERPHASE PROMETAPHASEPROPHASE
Centrosome Fragmentsof nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Nuclearenvelope
Spindlemicrotubules
Nucleolus
Centromere
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INTERPHASE
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PROPHASE
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PROMETAPHASE
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Interphase
– In the cytoplasm
– Cytoplasmic contents double
– Two centrosomes form
– In the nucleus
– Chromosomes duplicate during the S phase
– Nucleoli, sites of ribosome assembly, are visible
8.6 Cell division is a continuum of dynamic changes
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– Applying Your KnowledgeHuman cells have 46 chromosomes. By the end of interphase
– How many chromosomes are present in one cell?
– How many chromatids are present in one cell?
8.6 Cell division is a continuum of dynamic changes
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Prophase
– In the cytoplasm
– Microtubules begin to emerge from centrosomes, forming the spindle
– In the nucleus
– Chromosomes coil and become compact
– Nucleoli disappear
8.6 Cell division is a continuum of dynamic changes
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Prometaphase
– Spindle microtubules reach chromosomes, where they
– Attach at kinetochores on the centromeres of sister chromatids
– Move chromosomes to the center of the cell through associated protein ―motors‖
– Other microtubules meet those from the opposite poles
– The nuclear envelope disappears
8.6 Cell division is a continuum of dynamic changes
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Metaphaseplate
Nucleolusforming
METAPHASE TELOPHASE AND CYTOKINESISANAPHASE
Cleavagefurrow
Daughterchromosomes
NuclearenvelopeformingSpindle
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Metaphaseplate
Nucleolusforming
METAPHASE TELOPHASE AND CYTOKINESISANAPHASE
Cleavagefurrow
Daughterchromosomes
NuclearenvelopeformingSpindle
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METAPHASE
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ANAPHASE
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TELOPHASE AND CYTOKINESIS
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Metaphase
– Spindle is fully formed
– Chromosomes align at the cell equator
– Kinetochores of sister chromatids are facing the opposite poles of the spindle
– Applying Your KnowledgeBy the end of metaphase
– How many chromosomes are present in one human cell?
– How many chromatids are present in one human cell?
8.6 Cell division is a continuum of dynamic changes
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Anaphase
– Sister chromatids separate at the centromeres
– Daughter chromosomes are moved to opposite poles of the cell
– Motor proteins move the chromosomes along the spindle microtubules
– Kinetochore microtubules shorten
– The cell elongates due to lengthening of nonkinetochore microtubules
– Applying Your KnowledgeBy the end of anaphase
– How many chromosomes are present in one human cell?
– How many chromatids are present in one human cell?
8.6 Cell division is a continuum of dynamic changes
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Telophase
– The cell continues to elongate
– The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei
– Chromatin uncoils
– Nucleoli reappear
– The spindle disappears
– Applying Your KnowledgeBy the end of telophase
– How many chromosomes are present in one nucleus within the human cell?
– Are the nuclei identical or different?
8.6 Cell division is a continuum of dynamic changes
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Cytokinesis
– Cytoplasm is divided into separate cells
– Applying Your KnowledgeBy the end of cytokinesis
– How many chromosomes are present in one human cell?
– How many chromatids are present in one human cell?
8.6 Cell division is a continuum of dynamic changes
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Cytokinesis
– Cleavage in animal cells
– A cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin
– The cleavage furrow deepens to separate the contents into two cells
– Cytokinesis in plant cells
– A cell plate forms in the middle from vesicles containing cell wall material
– The cell plate grows outward to reach the edges, dividing the contents into two cells
– Each cell has a plasma membrane and cell wall
8.7 Cytokinesis differs for plant and animal cells
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Animation: Cytokinesis
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Cleavagefurrow
Contracting ring ofmicrofilaments
Daughter cells
Cleavage furrow
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Cleavagefurrow
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Contracting ring ofmicrofilaments
Daughter cells
Cleavage furrow
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Cell plate Daughter cells
Cell wall
Vesicles containingcell wall material
Daughter nucleus
Cell plateforming
Wall ofparent cell
New cell wall
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Daughter nucleus
Cell plateforming
Wall ofparent cell
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Cell plate Daughter cells
Cell wall
Vesicles containingcell wall material
New cell wall
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Factors that control cell division
– Presence of essential nutrients
– Growth factors, proteins that stimulate division
– Presence of other cells causes density-dependent inhibition
– Contact with a solid surface; most cells show anchorage dependence
8.8 Anchorage, cell density, and chemical growthfactors affect cell division
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Culture of cells
Addition ofgrowthfactor
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Cells anchor todish surfaceand divide.
When cells haveformed a completesingle layer, theystop dividing (density-dependent inhibition).
If some cells arescraped away, theremaining cells divideto fill the dish with asingle layer and thenstop (density-dependent inhibition).
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Cell cycle control system
– A set of molecules, including growth factors, that triggers and coordinates events of the cell cycle
Checkpoints
– Control points where signals regulate the cell cycle
– G1 checkpoint allows entry into the S phase or causes the cell to leave the cycle, entering a nondividing G0 phase
– G2 checkpoint
– M checkpoint
8.9 Growth factors signal the cell cycle control system
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G1 checkpoint
Controlsystem
M
S
G2
G1
M checkpoint
G2 checkpoint
G0
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Effects of a growth factor at the G1 checkpoint
– A growth factor binds to a receptor in the plasma membrane
– Within the cell, a signal transduction pathway propagates the signal through a series of relay molecules
– The signal reaches the cell cycle control system to trigger entry into the S phase
8.9 Growth factors signal the cell cycle control system
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G1 checkpoint
Controlsystem
M
S
G2
G1
Receptorprotein
Signaltransductionpathway
Relayproteins
Plasma membrane
Growth factor
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Cancer cells escape controls on the cell cycle
– Cancer cells divide rapidly, often in the absence of growth factors
– They spread to other tissues through the circulatory system
– Growth is not inhibited by other cells, and tumorsform
– Benign tumors remain at the original site
– Malignant tumors spread to other locations by metastasis
8.10 CONNECTION: Growing out of control, cancer cells produce malignant tumors
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Cancer treatments
– Localized tumors can be treated with surgery or radiation
– Chemotherapy is used for metastatic tumors
8.10 CONNECTION: Growing out of control, cancer cells produce malignant tumors
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Classification of cancer by origin
– Carcinomas arise in external or internal body coverings
– Sarcomas arise in supportive and connective tissue
– Leukemias and lymphomas arise from blood-forming tissues
8.10 CONNECTION: Growing out of control, cancer cells produce malignant tumors
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A tumor grows from asingle cancer cell.
Cancer cells spreadthrough lymph andblood vessels toother parts of the body.
Cancer cells invadeneighboring tissue.
Tumor
Glandulartissue
Lymphvessels
Bloodvessel
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Mitosis produces genetically identical cells for
– Growth
– Replacement
– Asexual reproduction
8.11 Review: Mitosis provides for growth, cell replacement, and asexual reproduction
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Video: Hydra Budding
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MEIOSIS AND CROSSING OVER
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Somatic cells have pairs of homologous chromosomes, receiving one member of each pair from each parent
Homologous chromosomes are matched in
– Length
– Centromere position
– Gene locations
– A locus (plural, loci) is the position of a gene
– Different versions of a gene may be found at the same locus on maternal and paternal chromosomes
8.12 Chromosomes are matched in homologous pairs
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The human sex chromosomes X and Y differ in size and genetic composition
Pairs of autosomes have the same size and genetic composition
Applying Your Knowledge
– Humans have 46 chromosomes; how many homologous pairs does that represent?
– If there is one pair of sex chromosomes, how many pairs of autosomes are found in humans?
8.12 Chromosomes are matched in homologous pairs
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Sister chromatids One duplicatedchromosome
Centromere
Homologous pair ofchromosomes
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Meiosis is a process that converts diploid nuclei to haploid nuclei
– Diploid cells have two homologous sets of chromosomes
– Haploid cells have one set of chromosomes
– Meiosis occurs in the sex organs, producing gametes—sperm and eggs
Fertilization is the union of sperm and egg
– The zygote has a diploid chromosome number, one set from each parent
8.13 Gametes have a single set of chromosomes
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Haploid gametes (n = 23)
nEgg cell
Sperm cellFertilizationMeiosis
Multicellulardiploid adults
(2n = 46)
Mitosis anddevelopment
n
2n
Diploidzygote
(2n = 46)
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Like mitosis, meiosis is preceded by interphase
– Chromosomes duplicate during the S phase
Unlike mitosis, meiosis has two divisions
– During meiosis I, homologous chromosomes separate
– The chromosome number is reduced by half
– During meiosis II, sister chromatids separate
– The chromosome number remains the same
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Events in the nucleus during meiosis I
– Prophase I
– Chromosomes coil and become compact
– Homologous chromosomes come together as pairs by synapsis
– Each pair, with four chromatids, is called a tetrad
– Nonsister chromatids exchange genetic material by crossing over
8.14 Meiosis reduces the chromosome number from diploid to haploid
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– Applying Your KnowledgeHuman cells have 46 chromosomes. At the end of prophase I
– How many chromosomes are present in one cell?
– How many chromatids are present in one cell?
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Events in the nucleus during meiosis I
– Metaphase I
– Tetrads align at the cell equator
– Anaphase I
– Homologous pairs separate and move toward opposite poles of the cell
– Applying Your Knowledge Human cells have 46 chromosomes. At the end of Metaphase I
– How many chromosomes are present in one cell?
– How many chromatids are present in one cell?
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Events in the nucleus during meiosis I
– Telophase I
– Duplicated chromosomes have reached the poles
– A nuclear envelope forms around chromosomes in some species
– Each nucleus has the haploid number of chromosomes
– Applying Your KnowledgeAfter telophase I and cytokinesis
– How many chromosomes are present in one human cell?
– How many chromatids are present in one human cell?
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Centrosomes(with centriolepairs)
PROPHASE I
Microtubules
attached to
kinetochore
INTERPHASE
Sites of crossing overMetaphaseplate
Spindle
MEIOSIS I: Homologous chromosomes separate
METAPHASE I
Sister chromatidsremain attached
ANAPHASE I
Nuclearenvelope
Sisterchromatids
Centromere(with kinetochore)
Homologouschromosomes separateChromatin
Tetrad
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Meiosis II follows meiosis I without chromosome duplication
Each of the two haploid products enters meiosis II
Events in the nucleus during meiosis II
– Prophase II
– Chromosomes coil and become compact
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Events in the nucleus during meiosis II
– Metaphase II
– Duplicated chromosomes align at the cell equator
– Anaphase II
– Sister chromatids separate and chromosomes move toward opposite poles
8.14 Meiosis reduces the chromosome number from diploid to haploid
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Events in the nucleus during meiosis II
– Telophase II
– Chromosomes have reached the poles of the cell
– A nuclear envelope forms around each set of chromosomes
– With cytokinesis, four haploid cells are produced
– Applying Your KnowledgeAfter telophase II and cytokinesis
– How many chromosomes are present in one human cell?
– How many chromatids are present in one human cell?
8.14 Meiosis reduces the chromosome number from diploid to haploid
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PROPHASE I
MEIOSIS II: Sister chromatids separate
METAPHASE II ANAPHASE II
Cleavagefurrow
TELOPHASE II
AND CYTOKINESIS
Sister chromatidsseparate
Haploid daughtercells forming
TELOPHASE II
AND CYTOKINESIS
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Which characteristics are similar for mitosis and meiosis?
– One duplication of chromosomes
Which characteristics are unique to meiosis?
– Two divisions of chromosomes
– Pairing of homologous chromosomes
– Exchange of genetic material by crossing over
8.15 Mitosis and meiosis have important similarities and differences
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What is the outcome of each process?
– Mitosis: two genetically identical cells, with the same chromosome number as the original cell
– Meiosis: four genetically different cells, with half the chromosome number of the original cell
8.15 Mitosis and meiosis have important similarities and differences
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Prophase
Metaphase IMetaphase
2n = 4
Tetradsalign at themetaphase plate
Duplicatedchromosome(two sisterchromatids)
Parent cell(before chromosome duplication)
Chromosomeduplication
Chromosomesalign at themetaphase plate
AnaphaseTelophase Sister chromatids
separate duringanaphase
Daughter cellsof mitosis
2n 2n
n
Chromosomeduplication
Site ofcrossing over
Tetrad formedby synapsis ofhomologouschromosomes
MEIOSIS
Prophase I
Anaphase I
Telophase I
MITOSIS
MEIOSIS I
Haploid
n = 2
Daughtercells of
meiosis I
MEIOSIS II
n n n
Daughter cells of meiosis II
Homologouschromosomesseparate(anaphase I);sister chroma-tids remaintogether
No furtherchromosomalduplication;sisterchromatidsseparate(anaphase II)
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Animation: Genetic Variation
Independent orientation at metaphase I
– Each pair of chromosomes independently aligns at the cell equator
– There is an equal probability of the maternal or paternal chromosome facing a given pole
– The number of combinations for chromosomes packaged into gametes is 2n where n = haploid number of chromosomes
Random fertilization
– The combination of each unique sperm with each unique egg increases genetic variability
8.16 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
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Two equally probablearrangements ofchromosomes at
metaphase I
Possibility 1 Possibility 2
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Two equally probablearrangements ofchromosomes at
metaphase I
Possibility 1 Possibility 2
Metaphase II
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Two equally probablearrangements ofchromosomes at
metaphase I
Possibility 1 Possibility 2
Metaphase II
Combination 1
Gametes
Combination 2 Combination 3 Combination 4
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8.17 Homologous chromosomes can carry different versions of genes
Separation of homologous chromosomes during meiosis can lead to genetic differences between gametes
– Homologous chromosomes may have different versions of a gene at the same locus
– One version was inherited from the maternal parent, and the other came from the paternal parent
– Since homologues move to opposite poles during anaphase I, gametes will receive either the maternal or paternal version of the gene
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Brown coat (C); black eyes (E) White coat (c); pink eyes (e)
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Brown coat (C); black eyes (E)
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White coat (c); pink eyes (e)
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Tetrad in parent cell(homologous pair of
duplicated chromosomes)
Coat-colorgenes
Chromosomes ofthe four gametes
Meiosis
PinkWhite
BlackBrown
Eye-colorgenes
C
e
E
c
C
e
E
c
C
e
E
c
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Genetic recombination is the production of new combinations of genes due to crossing over
Crossing over involves exchange of genetic material between homologous chromosomes
– Nonsister chromatids join at a chiasma (plural, chiasmata), the site of attachment and crossing over
– Corresponding amounts of genetic material are exchanged between maternal and paternal (nonsister) chromatids
8.18 Crossing over further increases genetic variability
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Animation: Crossing Over
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Centromere
ChiasmaTetrad
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Breakage of homologous chromatids
Coat-colorgenes
Eye-colorgenes
C
(homologous pair of
chromosomes in synapsis)
E
c e
1
Tetrad
C E
c e
Joining of homologous chromatids2
Separation of homologous
chromosomes at anaphase I3
C E
c e
Chiasma
Separation of chromatids at
anaphase II and
completion of meiosis
4
C E
c e
c E
C e
c e
c E
C E
C e
Parental type of chromosome
Gametes of four genetic types
Recombinant chromosome
Parental type of chromosome
Recombinant chromosome
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Breakage of homologous chromatids
Coat-colorgenes
Eye-colorgenes
C
(homologous pair of
chromosomes in synapsis)
E
c e
Tetrad
C E
c e
Joining of homologous chromatids2
C E
c e
Chiasma
1
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Separation of homologous
chromosomes at anaphase I
C E
c e
Chiasma
Separation of chromatids at
anaphase II and
completion of meiosis
C E
c e
c E
C e
c e
c E
C E
C e
Parental type of chromosome
Gametes of four genetic types
Recombinant chromosome
Parental type of chromosome
Recombinant chromosome
4
3
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ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE
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A karyotype shows stained and magnified versions of chromosomes
– Karyotypes are produced from dividing white blood cells, stopped at metaphase
– Karyotypes allow observation of
– Homologous chromosome pairs
– Chromosome number
– Chromosome structure
8.19 A karyotype is a photographic inventory of an individual’s chromosomes
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Packed redand white bloodcells
CentrifugeBloodculture
Fluid1
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Packed redand white bloodcells
CentrifugeBloodculture
Fluid1
Hypotonicsolution
2
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Packed redand white bloodcells
CentrifugeBloodculture
Fluid1
Hypotonicsolution
2
3
Fixative
Whitebloodcells
Stain
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4
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Centromere
Sisterchromatids
Pair of homologouschromosomes
5
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Trisomy 21 involves the inheritance of three copies of chromosome 21
– Trisomy 21 is the most common human chromosome abnormality
– An imbalance in chromosome number causes Downsyndrome, which is characterized by
– Characteristic facial features
– Susceptibility to disease
– Shortened life span
– Mental retardation
– Variation in characteristics
– The incidence increases with the age of the mother
8.20 CONNECTION: An extra copy of chromosome 21 causes Down syndrome
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Infa
nts
wit
h D
ow
n s
yn
dro
me
(per
1,0
00 b
irth
s)
Age of mother
90
70
60
50
40
30
20
10
0
80
20 40353025 5045
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Nondisjunction is the failure of chromosomes or chromatids to separate during meiosis
– During Meiosis I
– Both members of a homologous pair go to one pole
– During Meiosis II
– Both sister chromatids go to one pole
Fertilization after nondisjunction yields zygotes with altered numbers of chromosomes
8.21 Accidents during meiosis can alter chromosome number
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Nondisjunctionin meiosis I
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Nondisjunctionin meiosis I
Normalmeiosis II
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Nondisjunctionin meiosis I
Normalmeiosis II
n + 1
Gametes
Number of chromosomes
n + 1 n – 1 n – 1
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Normalmeiosis I
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Nondisjunctionin meiosis II
Normalmeiosis I
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Nondisjunctionin meiosis II
Normalmeiosis I
Gametes
Number of chromosomes
n + 1 n – 1 n n
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Sex chromosome abnormalities tend to be less severe as a result of
– Small size of the Y chromosome
– X-chromosome inactivation
– In each cell of a human female, one of the two X chromosomes becomes tightly coiled and inactive
– This is a random process that inactivates either the maternal or paternal chromosome
– Inactivation promotes a balance between the number of X chromosomes and autosomes
8.22 CONNECTION: Abnormal numbers of sexchromosomes do not usually affect survival
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Polyploid species have more than two chromosome sets
– Observed in many plant species
– Seen less frequently in animals
Example
– Diploid gametes are produced by failures in meiosis
– Diploid gamete + Diploid gamete Tetraploid offspring
– The tetraploid offspring have four chromosome sets
8.23 EVOLUTION CONNECTION: New species can arise from errors in cell division
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Structure changes result from breakage and rejoining of chromosome segments
– Deletion is the loss of a chromosome segment
– Duplication is the repeat of a chromosome segment
– Inversion is the reversal of a chromosome segment
– Translocation is the attachment of a segment to a nonhomologous chromosome; can be reciprocal
Altered chromosomes carried by gametes cause birth defects
Chromosomal alterations in somatic cells can cause cancer
8.24 CONNECTION: Alterations of chromosome structure can cause birth defects and cancer
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Deletion
Inversion
Duplication
Homologouschromosomes
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Reciprocaltranslocation
Nonhomologouschromosomes
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Chromosome 9
“Philadelphia chromosome”
Activated cancer-causing gene
Reciprocaltranslocation
Chromosome 22
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Mitosis(division
of nucleus)
GeneticallyIdentical“daughtercells”
S(DNA synthesis)
G1
G2Cytokinesis
(division of cytoplasm)
INTERPHASE (cell growth and chromosome duplication)
MITOTIC PHASE (M)
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Haploid gametes (n = 23)
nEgg cell
Sperm cell
FertilizationMeiosis
Multicellulardiploid adults
(2n = 46)
Mitosis and development
n
2nDiploidzygote
(2n = 46)
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1. Identify the roles of cell division in living organisms
2. Distinguish between events in interphase, mitosis, and cytokinesis
3. Describe the movements of chromosomes in prophase, metaphase, anaphase, and telophase of mitosis
4. Define the following terms: checkpoint, chiasma, chromosome, chromatid, centromere, crossing over, homologous chromosome pair, nondisjunction, and spindle
You should now be able to
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5. Compare and contrast the processes of mitosis and meiosis
6. Distinguish between terms in the following groups: haploid—diploid; sister chromatids—nonsister chromatids;deletion—duplication—inversion—translocation
7. Describe how genetic variability is generated through meiosis and fertilization
8. Identify factors that control cell division and describe how cancer cells escape these controls
You should now be able to
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