Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 18
Patterns of
Chromosome Inheritance
Lecture Outline
Part 2
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18.3 Mitosis
Overview of mitosis
• A diploid cell makes and divides an exact
copy of its nucleus.
• It is used in cell ________ and cell ________.
• Mitosis occurs in body cells.
• There are 4 phases.
1.
2.
3.
4.
Prophase
Metaphase
Anaphase
Telophase
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18.3 Mitosis
Overview of mitosis
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centrosome
centriole
chromosome
2n = 4
DNA REPLICATION
DURING INTERPHASE
duplicated
chromosome
consisting of
two sister
chromatids
centromere
2n = 4
MITOSIS
Figure 18.6 An overview of mitosis.
2n = 4
2n = 4
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18.3 Mitosis
1. Mitosis: Prophase
• Chromosomes ________ and become visible.
• The _________________ fragments.
• The ___________ disappears.
• Centrosomes move to __________ poles.
• __________ fibers appear and attach to the
centromeres.
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18.3 Mitosis
1. Mitosis: Prophase
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aster
duplicated
chromosomes
20 µm
nuclear
envelope
fragments
20 µm
centromere
chromatin
condenses
nucleolus
disappears
spindle
fibers forming
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
(early prophase, prophase): © Ed Reschke
Figure 18.8 The phases of mitosis.
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18.3 Mitosis
2. Mitosis: Metaphase
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• Chromosomes
line up at the
middle of the
cell (equator).
spindle
pole
9 μm
chromosomes
at equator
20 μm
centromere
• Spindle
becomes fullyformed.
spindle fiber
Early Metaphase
Each chromatid is attached
to a spindle fiber. Some
spindle fibers stretch from each
spindle pole and overlap.
Figure 18.8 The phases of mitosis.
Metaphase
Centromeres of duplicated chromosomes
area lined at the equator (center of
fully formed spindle). Spindle fibers
attached to the sister chromatids
come from opposite spindle poles.
(metaphase): © Ed Reschke; (early metaphase): © Michael Abbey/Photo Researchers, Inc.
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18.3 Mitosis
3. Mitosis: Anaphase
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• Sister chromatids
separate at the
___________ and
move towards the
poles.
daughter chromosome 20 μm
spindle fiber
Anaphase
Sister chromatids part and become daughter
chromosomes that move toward the spindle
poles. In this way, each pole receives the same
number and kinds of chromosomes as the parental cell.
Figure 18.8 The phases of mitosis.
(anaphase): © Ed Reschke;
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18.3 Mitosis
4. Mitosis: Telophase and cytokinesis
•
•
•
•
•
•
Chromosomes arrive at
the poles.
Chromosomes become
indistinct chromatin again.
________ reappear.
Spindle ___________.
Nuclear envelope
_______________.
2 ___________ cells are
formed by a ring of actin
filaments (cleavage
furrow).
Figure 18.8 The phases of mitosis.
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cleavage furrow
16 μm
nucleolus
Telophase
Daughter cells are forming
as nuclear envelopes and
nucleoli reappear. Chromosomes will
become indistinct chromatin.
(telophase): © Ed Reschke;
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18.4 Meiosis
Overview of meiosis
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• __ nuclear divisions
occur to make 4
________ cells.
• It is used to make
gametes (egg and
sperm).
• Meiosis occurs in ___
_______
• Has 8 phases (4 in
each meiosis, I & II)
centromere
homologous
chromosome pair
nucleolus
centrioles
homologous
chromosome
pair
2n = 4
CHROMOSOME REPLICATION
synapsis
2n = 4
sister
chromatids
MEIOSIS I
Duplicated
homologous pairs
synapse and
then separate.
MEIOSIS II
Sister chromatids
separate, becoming
daughter chromosomes.
Figure 18.9 The results of meiosis.
n=2
n=2
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18.4 Meiosis
Meiosis I
•
•
•
•
Prophase I
– Homologous chromosomes pair (synapsis);
______________ occurs, in which there is
exchange of genetic information.
Metaphase I
– Homologous pairs line up at the _________.
Anaphase I
– Homologous chromosomes separate and move
toward opposite poles.
Telophase I
– 2 ____________ cells result, each with 23
____________ chromosomes.
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18.4 Meiosis
Meiosis I
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diploid
Prophase I
Chromosomes have duplicated. Homologous
chromosomes pair during synapsis and
crossing-over occurs.
Figure 18.10 The phases of meiosis.
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18.4 Meiosis
Meiosis I
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diploid
Prophase I
Chromosomes have duplicated. Homologous
chromosomes pair during synapsis and
crossing-over occurs.
Metaphase I
Homologous pairs align
independently at the equator.
Figure 18.10 The phases of meiosis.
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18.4 Meiosis
Meiosis I
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diploid
Prophase I
Chromosomes have duplicated. Homologous
chromosomes pair during synapsis and
crossing-over occurs.
Metaphase I
Homologous pairs align
independently at the equator.
Anaphase I
Homologous chromosomes separate
and move toward the poles.
Figure 18.10 The phases of meiosis.
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18.4 Meiosis
Meiosis I
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
diploid
Prophase I
Chromosomes have duplicated. Homologous
chromosomes pair during synapsis and
crossing-over occurs.
Metaphase I
Homologous pairs align
independently at the equator.
Anaphase I
Homologous chromosomes separate
and move toward the poles.
Telophase I
Daughter cells have one chromosome
from each homologous pair.
Figure 18.10 The phases of meiosis.
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18.4 Meiosis
Meiosis I
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
diploid
Prophase I
Chromosomes have duplicated. Homologous
chromosomes pair during synapsis and
crossing-over occurs.
Metaphase I
Homologous pairs align
independently at the equator.
Anaphase I
Homologous chromosomes separate
and move toward the poles.
haploid
Telophase I
Daughter cells have one chromosome
from each homologous pair.
Interkinesis
Chromosomes still
consist of two chromatids.
haploid
Figure 18.10 The phases of meiosis.
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