1. Chapter 8 The Cellular Basis of Reproduction and Inheritance
Cancer cells
start out as normal body cells,
undergo genetic mutations,
lose the ability to control the tempo of their own division, and
run amok, causing disease.
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2. Introduction In a healthy body, cell division allows for
In a healthy body, cell division allows for
growth,
the replacement of damaged cells, and
development from an embryo into an adult.
In sexually reproducing organisms, eggs and sperm result from
mitosis and
meiosis.
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3. CELL DIVISION AND REPRODUCTION
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4. 8.1 Cell division plays many important roles in the lives of organisms
Organisms reproduce their own kind, a key characteristic of life.
Cell division
is reproduction at the cellular level,
requires the duplication of chromosomes, and
sorts new sets of chromosomes into the resulting pair of daughter cells.
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5. 8.1 Cell division plays many important roles in the lives of organisms
Cell division is used
for reproduction of single-celled organisms,
growth of multicellular organisms from a fertilized egg into an adult,
repair and replacement of cells, and
sperm and egg production.
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6. 8.1 Cell division plays many important roles in the lives of organisms
Living organisms reproduce by two methods.
Asexual reproduction
produces offspring that are identical to the original cell or organism and
involves inheritance of all genes from one parent.
Sexual reproduction
produces offspring that are similar to the parents, but show variations in traits and
involves inheritance of unique sets of genes from two parents.
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7. Figure 8.1A Yeast cell asexually reproducing
Figure 8.1A A yeast cell producing a genetically identical daughter cell by asexual reproduction 7

8. Figure 8.1B Sea star reproducing asexually
Figure 8.1B A sea star reproducing asexually 8

9. Figure 8.1C African violet leaf cutting reproducing asexually
Figure 8.1C An African violet reproducing asexually from a cutting (the large leaf on the left) 9

10. Figure 8.1D Sexual reproduction produces offspring that are similar to the parents, but show variations in traits
Figure 8.1D Sexual reproduction produces offspring with unique combinations of genes. 10

11. 8.2 Prokaryotes reproduce by binary fission
Prokaryotes (bacteria and archaea) reproduce by binary fission (“dividing in half”).
The chromosome of a prokaryote is
a singular circular DNA molecule associated with proteins and
much smaller than those of eukaryotes.
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12. 8.2 Prokaryotes reproduce by binary fission
Binary fission of a prokaryote occurs in three stages:
duplication of the chromosome and separation of the copies,
continued elongation of the cell and movement of the copies, and
division into two daughter cells.
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13. Duplication of the chromosome and separation of the copies
Figure 8.2A_s1
Plasma
membrane
Prokaryotic
chromosome
Cell wall
Duplication of the chromosome
and separation of the copies 1
Figure 8.2A_s1 Binary fission of a prokaryotic cell (step 1) 13

14. Duplication of the chromosome and separation of the copies
Figure 8.2A_s2
Plasma
membrane
Prokaryotic
chromosome
Cell wall
Duplication of the chromosome
and separation of the copies 1
Continued elongation of the
cell and movement of the copies 2
Figure 8.2A_s2 Binary fission of a prokaryotic cell (step 2) 14

15. Division into two daughter cells
Figure 8.2A
Plasma
membrane
Prokaryotic
chromosome
Cell wall
Duplication of the chromosome
and separation of the copies 1
Continued elongation of the
cell and movement of the copies 2
Figure 8.2A_s3 Binary fission of a prokaryotic cell (step 3)
Division into
two daughter cells 3 15

16. THE EUKARYOTIC CELL CYCLE AND MITOSIS
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17. 8.3 The large, complex chromosomes of eukaryotes duplicate with each cell division
Eukaryotic cells
are more complex and larger than prokaryotic cells,
have more genes, and
store most of their genes on multiple chromosomes within the nucleus.
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18. 8.3 The large, complex chromosomes of eukaryotes duplicate with each cell division
Eukaryotic chromosomes are composed of chromatin consisting of
one long DNA molecule and
proteins that help maintain the chromosome structure and control the activity of its genes.
To prepare for division, the chromatin becomes
highly compact and
visible with a microscope.
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19. Figure 8.3A A plant cell (from an African blood lily) just before cell division19

20. Chromosomes DNA molecules Sister chromatids Chromosome duplication
Figure 8.3B
Chromosomes
DNA molecules
Sister
chromatids
Chromosome
duplication
Sister
chromatids
Centromere
Figure 8.3B Chromosome duplication and distribution
Chromosome
distribution
to the
daughter
cells 20

21. 8.3 The large, complex chromosomes of eukaryotes duplicate with each cell division
Before a eukaryotic cell begins to divide, it duplicates all of its chromosomes, resulting in
two copies called sister chromatids
joined together by a narrowed “waist” called the centromere.
When a cell divides, the sister chromatids
separate from each other, now called chromosomes, and
sort into separate daughter cells.
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22. 8.4 The cell cycle multiplies cells
The cell cycle is an ordered sequence of events that extends
from the time a cell is first formed from a dividing parent cell
until its own division.
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23. 8.4 The cell cycle multiplies cells
The cell cycle consists of two stages, characterized as follows:
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
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24. I N T E R P H A S G1 (first gap) S (DNA synthesis) M G2 (second gap)
Figure 8.4 I N T E R P H A S G1
(first gap) S
(DNA synthesis) M
Cytokinesis G2
(second gap)
Mitosis
Figure 8.4 The eukaryotic cell cycle T MI O IC PH A SE 24

25. 8.5 Cell division is a continuum of dynamic changes
Mitosis progresses through a series of stages:
prophase,
metaphase,
anaphase, and
telophase.
Cytokinesis occurs at end of telophase.
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26. 8.5 Cell division is a continuum of dynamic changes
A mitotic spindle is
required to divide the chromosomes,
composed of microtubules, and
produced by centrosomes, structures in the cytoplasm that
organize microtubule arrangement and
contain a pair of centrioles in animal cells.
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27. (with centriole pairs) Fragments of the nuclear envelope Early mitotic
Figure 8.5
MITOSIS
INTERPHASE
Prophase
Prometaphase
Centrosomes
(with centriole pairs)
Fragments of
the nuclear
envelope
Early mitotic
spindle
Centrosome
Kinetochore
Centrioles
Chromatin
Figure 8.5_1 The stages of cell division by mitosis: Interphase through Prometaphase
Centromere
Nuclear
envelope
Plasma
membrane
Chromosome,
consisting of two
sister chromatids
Spindle
microtubules 27

28. 8.5 Cell division is a continuum of dynamic changes
Interphase
The cytoplasmic contents double in G phases,
two centrosomes containing ____ form,
chromatin duplicates in the nucleus during the S phase
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29. 8.5 Cell division is a continuum of dynamic changes
Prophase
In the cytoplasm microtubules begin to emerge from centrosomes, forming the ____.
In the nucleus
chromatin coils and becomes compact to form ____.
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30. 8.5 Cell division is a continuum of dynamic changes
Metaphase
Spindle microtubules reach chromosomes, where they
attach on the centromeres and move ____ to the center of the cell
The nuclear envelope disappears.
____ align at the cell equator.
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31. (with centriole pairs) Early mitotic spindle Fragments of
Figure 8.5
MITOSIS
INTERPHASE
Prophase
Prometaphase
Centrosomes
(with centriole pairs)
Early mitotic
spindle
Fragments of
the nuclear envelope
Centrosome
Chromatin
Centrioles
Kinetochore
Figure 8.5_left The stages of cell division by mitosis: Interphase through Prometaphase
Nuclear
envelope
Plasma
membrane
Centromere
Chromosome,
consisting of two
sister chromatids
Spindle
microtubules 31

32. Telophase and Cytokinesis
Figure 8.5
MITOSIS
Metaphase
Anaphase
Telophase and Cytokinesis
Metaphase
plate
Cleavage
furrow
Figure 8.5_right The stages of cell division by mitosis: Metaphase through Cytokenesis
Mitotic
spindle
Nuclear
envelope
forming
Daughter
chromosomes 32

33. 8.5 Cell division is a continuum of dynamic changes
Anaphase
Sister chromatids separate at the centromeres.
Daughter chromosomes are moved to opposite poles of the cell as ____ shortens.
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34. Figure 8.5
Figure 8.5_7 The stages of cell division by mitosis: Anaphase
Anaphase 34

35. 8.5 Cell division is a continuum of dynamic changes
Telophase
The cell continues to elongate.
The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei.
Chromosomes uncoil to form ____.
The spindle breaks down.
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36. Telophase and Cytokinesis
Figure 8.5
Figure 8.5_8 The stages of cell division by mitosis: Telophase and Cytokenesis
Telophase and Cytokinesis 36

37. 8.5 Cell division is a continuum of dynamic changes
During cytokinesis, the cytoplasm is divided into separate cells.
The process of cytokinesis differs in animal and plant cells.
Teaching Tips
Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
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38. 8.6 Cytokinesis differs for plant and animal cells
In animal cells, cytokinesis occurs as
a cleavage ____ forms and deepens to separate the contents into two cells.
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39. Cleavage furrow Daughter cells
Figure 8.6A
Cytokinesis
Cleavage
furrow
Daughter
cells
Figure 8.6A Cleavage of an animal cell
Cleavage
furrow 39

40. 8.6 Cytokinesis differs for plant and animal cells
In plant cells, cytokinesis occurs as
a cell plate forms in the middle
the cell plate grows outward to reach the edges, dividing the contents into two cells,
each cell now possesses a plasma membrane and cell ____.
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41. Cytokinesis New cell wall Cell wall of the parent cell Cell wall
Figure 8.6B
Cytokinesis
New
cell wall
Cell wall
of the
parent cell
Cell wall
Plasma
membrane
Daughter
nucleus
Vesicles
containing
cell wall
material
Cell plate
Daughter
cells
Figure 8.6B Cell plate formation in a plant cell
Cell plate
forming 41

42. 8.9 CONNECTION: Growing out of control, cancer cells produce malignant tumors
Cancer currently claims the lives of 20% of the people in the United States and other industrialized nations.
Cancer cells escape controls on the cell cycle.
Cancer cells
Undergo mitosis rapidly
spread to other tissues through the circulatory system, and
grow without being inhibited by other cells.
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43. 8.9 CONNECTION: Growing out of control, cancer cells produce malignant tumors
A tumor is an abnormally growing mass of body cells.
Benign tumors remain at the original site.
Malignant tumors spread to other locations, called metastasis.
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44. Lymph vessels Blood vessel Tumor Tumor in another part of the body
Figure 8.9
Lymph
vessels
Blood
vessel
Tumor
Tumor in
another
part of
the body
Glandular
tissue
Figure 8.9 Growth and metastasis of a malignant (cancerous) tumor of the breast
Growth
Invasion
Metastasis 44

45. 8.9 CONNECTION: Growing out of control, cancer cells produce malignant tumors
Cancer treatments
Localized tumors can be
removed surgically and/or
treated with concentrated beams of high-energy radiation.
Chemotherapy is used for metastatic tumors.
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46. 8.10 Review: Mitosis provides for growth, cell replacement, and asexual reproduction
When the cell cycle operates normally, mitosis produces genetically identical cells for
growth,
replacement of damaged and lost cells, and
asexual reproduction.
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47. Laboratory--Onion growing by mitosis
Figure 8.10A Growth (in an onion root) 47

48. MEIOSIS AND CROSSING OVER
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49. 8.11 Chromosomes are matched in homologous pairs
In humans, somatic cells have
23 pairs of homologous chromosomes and
one member of each pair from each parent.
The human sex chromosomes X and Y differ in size and genetic composition.
The other 22 pairs of chromosomes are autosomes with the same size and genetic composition.
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50. 8.11 Chromosomes are matched in homologous pairs
Homologous chromosomes are matched in
length,
centromere position, and
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.
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51. Pair of homologous chromosomes One duplicated chromosome
Figure 8.11
Pair of homologous
chromosomes
Locus
Centromere
Sister
chromatids
Figure 8.11 A pair of homologous chromosomes
One duplicated
chromosome 51

52. 8.12 Gametes have a single set of chromosomes
An organism’s life cycle is the sequence of stages leading
from the adults of one generation
to the adults of the next.
Humans and many animals and plants are diploid, with body cells that have
two sets of chromosomes,
one from each parent.
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53. 8.12 Gametes have a single set of chromosomes
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.
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54. Multicellular diploid adults (2n  46) Diploid stage (2n)
Figure 8.12A
Haploid gametes (n  23) n
Egg cell n
Sperm cell
Meiosis
Fertilization
Ovary
Testis
Figure 8.12A The human life cycle
Diploid
zygote
(2n  46) 2n
Key
Mitosis
Haploid stage (n)
Multicellular diploid
adults (2n  46)
Diploid stage (2n) 54

55. 8.12 Gametes have a single set of chromosomes
All sexual life cycles include an alternation between
a diploid stage and
a haploid stage.
Producing haploid gametes prevents the chromosome number from doubling in every generation.
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56. Sister chromatids A pair of homologous chromosomes in a diploid
Figure 8.12B
INTERPHASE
MEIOSIS I
MEIOSIS II
Sister
chromatids 1 2 3
A pair of
homologous
chromosomes
in a diploid
parent cell
A pair of
duplicated
homologous
chromosomes
Figure 8.12B How meiosis halves chromosome number 56

57. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis is a type of cell division that produces haploid gametes in diploid organisms.
Two haploid gametes combine in fertilization to restore the diploid state in the zygote.
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58. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis and mitosis are preceded by the duplication of chromosomes. However,
meiosis is followed by two consecutive cell divisions and
mitosis is followed by only one cell division.
Because in meiosis, one duplication of chromosomes is followed by two divisions, each of the four daughter cells produced has a haploid set of chromosomes.
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59. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis I – Prophase I – events occurring in the nucleus.
Chromosomes coil and become compact.
Homologous chromosomes come together as pairs
Each pair, with four chromatids, is called a tetrad.
Tetrads exchange genetic material by crossing over.
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60. MEIOSIS I: Homologous chromosomes separate
Figure 8.13
MEIOSIS I: Homologous chromosomes separate
INTERPHASE:
Chromosomes duplicate
Prophase I
Metaphase I
Anaphase I
Centrosomes
(with centriole
pairs)
Spindle microtubules
attached to a kinetochore
Sister chromatids
remain attached
Sites of crossing over
Centrioles
Spindle
Tetrad
Figure 8.13_left The stages of meiosis: Interphase and Meiosis I
Nuclear
envelope
Chromatin
Sister
chromatids
Centromere
(with a
kinetochore)
Metaphase
plate
Fragments
of the
nuclear
envelope
Homologous
chromosomes
separate 60

61. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis I – Metaphase I – Tetrads align at the cell equator.
Meiosis I – Anaphase I – Homologous pairs separate and move toward opposite poles of the cell.
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62. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis I – Telophase I
Duplicated chromosomes have reached the poles.
A nuclear envelope re-forms around chromosomes in some species.
Each nucleus has the haploid number of chromosomes.
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63. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis II follows meiosis I without chromosome duplication.
Each of the two haploid products enters meiosis II.
Meiosis II – Prophase II
Chromosomes coil and become compact (if uncoiled after telophase I).
Nuclear envelope, if re-formed, breaks up again.
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64. Figure 8.13
MEIOSIS II: Sister chromatids separate
Telophase II
and Cytokinesis
Telophase I and Cytokinesis
Prophase II
Metaphase II
Anaphase II
Cleavage
furrow
Sister chromatids
separate
Haploid daughter
cells forming
Figure 8.13_right The stages of meiosis: Telophase I and Meiosis II 64

65. 8.13 Meiosis reduces the chromosome number from diploid to haploid
Meiosis II – Metaphase II – Duplicated chromosomes align at the cell equator.
Meiosis II – Anaphase II
Sister chromatids separate and
chromosomes move toward opposite poles.
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66. 8.13 Meiosis reduces the chromosome number from diploid to haploid
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.
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67. 8.14 Mitosis and meiosis have important similarities and differences
Mitosis and meiosis both
begin with diploid parent cells that
have chromosomes duplicated during the previous interphase.
However the end products differ.
Mitosis produces two genetically identical diploid somatic daughter cells.
Meiosis produces four genetically unique haploid gametes.
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68. Sister chromatids are separated
Figure 8.14
MITOSIS
MEIOSIS I
Chromosomes are duplicated
Chromosomes are duplicated
Parent cell 2n = 4
Prophase
Prophase I
Homologous chromosomes pair up
Homologous chromosomes
remain separate
Crossing over
Metaphase
Metaphase I
Pairs of homologous chromosomes line up at the metaphase plate
Chromosomes line up at the metaphase plate
Anaphase Telophase
Anaphase I Telophase I
Homologous chromosomes are separated
Figure 8.14 Comparison of mitosis and meiosis
Sister chromatids are separated
Sister chromatids remain attached 2n 2n
n = 2
n = 2
MEIOSIS II
Sister chromatids are separated n n n n 68

69. MITOSIS MEIOSIS I MEIOSIS II Figure 8.14
One division of the nucleus and cytoplasm Result: Two genetically identical diploid cells Used for: Growth, tissue repair, asexual reproduction
Two divisions of the nucleus and cytoplasm Result: Four genetically unique haploid cells Used for: Sexual reproduction

70. 8.15 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
Genetic variation in gametes results from
independent orientation at metaphase I and
random fertilization.
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71. 8.15 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
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.
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72. 8.15 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
Random fertilization – The combination of each unique sperm with each unique egg increases genetic variability.
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73. Two equally probable arrangements of chromosomes at metaphase I
Figure 8.15
Possibility A
Possibility B
Two equally probable
arrangements of
chromosomes at
metaphase I
Figure 8.15_s1 Results of the independent orientation of chromosomes at metaphase I (step 1) 73

74. Two equally probable arrangements of chromosomes at metaphase I
Figure 8.15
Possibility A
Possibility B
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Figure 8.15_s2 Results of the independent orientation of chromosomes at metaphase I (step 2) 74

75. Two equally probable arrangements of chromosomes at metaphase I
Figure 8.15
Possibility A
Possibility B
Two equally probable
arrangements of
chromosomes at
metaphase I
Metaphase II
Figure 8.15_s3 Results of the independent orientation of chromosomes at metaphase I (step 3)
Gametes
Combination 1
Combination 2
Combination 3
Combination 4 75

76. 8.16 Homologous chromosomes may 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 ____ I, gametes will receive either the maternal or paternal version of the gene.
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77. duplicated chromosomes)
Figure 8.16
Coat-color
genes
Eye-color
genes C E
Brown
Black
Brown coat (C);
black eyes (E) C E C E
Meiosis c e c
Figure 8.16 Differing genetic information (coat color and eye color) on homologous chromosomes e c e
White
Pink
Tetrad in parent cell
(homologous pair of
duplicated chromosomes)
Chromosomes of
the four gametes
White coat (c);
pink eyes (e) 77

78. 8.17 Crossing over further increases genetic variability
Genetic recombination is the production of new combinations of genes due to crossing over.
Crossing over is an exchange of corresponding segments between chromatids on homologous chromosomes.
Corresponding amounts of genetic material are exchanged between maternal and paternal chromatids.
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79. Chiasma Sister chromatids Figure 8.17a-0 Figure 8.17A-B
Tetrad
(pair of homologous
chromosomes in synapsis) c e 1
Breakage of homologous chromatids
Chiasma C E c e 2
Joining of homologous chromatids C E
Sister chromatids c e 3
Separation of homologous
chromosomes at anaphase I C E C e c E
Figure 8.17B How crossing over leads to genetic recombination c e
Separation of chromatids at
anaphase II and
completion of meiosis 4 C E
Parental type of chromosome C e
Recombinant chromosome c E
Recombinant chromosome c e
Parental type of chromosome
Gametes of four genetic types 79

80. ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE
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81. 8.18 A karyotype is a photographic inventory of an individual’s chromosomes
A karyotype is an ordered display of magnified images of an individual’s chromosomes arranged in pairs.
Karyotypes
are often produced from dividing cells arrested at metaphase of mitosis and
allow for the observation of
homologous chromosome pairs,
chromosome number, and
chromosome structure.
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82. Figure 8.19
Figure 8.18_s4 Preparation of a karyotype from a blood sample (step 4) 4 82

83. Centromere Sister chromatids Pair of homologous chromosomes
Figure 8.19
Centromere
Sister
chromatids
Pair of
homologous
chromosomes
Figure 8.18_s5 Preparation of a karyotype from a blood sample (step 5) 5
Sex chromosomes 83

84. 8.19 CONNECTION: An extra copy of chromosome 21 causes Down syndrome
Trisomy 21
involves the inheritance of three copies of chromosome 21 and
is the most common human chromosome abnormality.
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85. 8.19 CONNECTION: An extra copy of chromosome 21 causes Down syndrome
Trisomy 21, called Down syndrome, produces a characteristic set of symptoms, which include:
mental retardation,
characteristic facial features,
short stature,
heart defects,
susceptibility to respiratory infections, leukemia, and Alzheimer’s disease, and
shortened life span.
The incidence increases with the age of the mother.
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86. A person with Down syndrome
Figure 8.20A
Trisomy 21
Figure 8.19A A karyotype showing trisomy 21, and an individual with Down syndrome
A person with Down syndrome 86

87. Infants with Down syndrome
Figure 8.20B 90 80 70 60 50
Infants with Down syndrome
(per 1,000 births) 40 30
Figure 8.19B Maternal age and incidence of Down syndrome 20 10 20 25 30 35 40 45 50
Age of mother 87

88. Figure from Laboratory
Figure 8.UN04 Testing Your Knowledge, question 12 88