Download Chapter 8 Cell Reproduction

Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Chapter 8
Cell Reproduction
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
First Human cell line
•In 1951, first
human cell line
HeLa was cultured
in the lab.
•HeLa cells were
generated from
the cervical tumor
tissue of Henrietta
Lacks.
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Key Questions
•How is cell division critical to the
lives of single-celled and
multicelled organisms?
•How do eukaryote cells divide
during mitosis and cytokinesis?
•How does the DNA fit into the
nucleus without becoming tangled?
•How do cells regulate the cell cycle?
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
How Do Cells Divide?
•Mitosis — simple division of a
cell into 2 new cells
•Provides for growth
•Creates replacements for cells
•In single celled organisms,
produces new individuals
•Cell copies DNA before it divides
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Tobin and Dusheck: Asking About Life, 3E
Early Info About
Chromosomes
Chapter 8
•Walther
Flemming
— detailed
description of
chromosomal
movement
during mitosis
•Did not know
role of nucleus
nor
chromosomes
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Discovering the Function of
Chromosomes
•At first, scientists assumed that
the chromosomes in a cell were all
alike
•19th century biologists did not
realize that chromosomes carry
hereditary information
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Tobin and Dusheck: Asking About Life, 3E
Discovering the Function of
Chromosomes
Chapter 8
•Wilhelm Roux noticed the complex
way the X-shaped chromosomes split
during mitosis
 August
Weismann
(1889) suggested the
nucleus contained
the hereditary
material; he called it
“
germ plasm”
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Cell reproduction
•The replication of DNA
•The equal distribution of DNA to
the two daughter cells
•The division of the rest of cell
material into tow daughter cells
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
How Do Prokaryotic
Cells Divide?
•Divide by binary fission
•Have only 1 chromosome,
no nuclear membrane
•Duplicate
chromosome
•Then, cell
pinches into 2
cells
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Karyotype
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Tobin and Dusheck: Asking About Life, 3E
Sock Karyotyping
Chapter 8
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
How Do Eukaryotic Cells Divide?
•More complicated process
•Have a nucleus with pairs of
homologous chromosomes — pairs
of matching chromosomes
•Cell cycle — Everything that
happens to a cell from the time it
first forms until it divides
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Cell Cycle
•Several phases
–M, mitosis
phase, includes
both mitosis
and cytokinesis
–Interphase
•G1 (gap or growth phase) cell doubles all
its materials
•S (synthesis) DNA replicates
•G2 (gap) assembles molecular machinery
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Copyright 2005—Brooks/Cole—Thomson Learning
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Mitosis Overview
•Continuous Process
•Has 4 phases:
–Prophase
–Metaphase
–Anaphase
–Telophase
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Prophase
•Replicated chromosomes
condensed and become visible
•Chromosomes appear as 2
chromatids
•Microtubule spindles appear;
centrioles appear
•Nuclear membrane disappears
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Metaphase
•Longest stage of mitosis
•Chromosomes line up between the
2 poles of the spindle
•Form a disc called the metaphase
plate
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Anaphase
•Chromatids separate
•Microtubules attached to the
centromeres shorten
•Separated chromosomes move
away from the metaphase plate
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Telophase
•Mitotic apparatus breaks down
•Chromosomes unwind
•Nucleus reappears with
membranes covering the 2 new
sets of chromosomes
•Each chromosome consists of only
1 chromatid-like structure
•Cytokinesis occurs
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Fitting DNA Into a Cell
•Proteins called histones pack the
DNA into small, tight bundles
called nucleosomes
•Strings of nucleosomes fold and
loop to form chromosomes that fit
into the cell
•No one knows exactly how this
occurs
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Cytokinesis
•In animal cells,
actin filaments
form a
contractile ring
that pinches the
cytoplasm in 2
•In plant cells, telophase
includes the building of
new cell membranes and
cell walls
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
New Cell Wall
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Mitosis Mindbenders
•A human cell has 46
chromosomes in its cells. After
the S phase of the cell cycle,
how many chromosomes will the
cell contain?
•How many homologous pairs of
chromosomes will the cell have
at prophase?
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
When Do Cells
Stop Dividing?
•Cell senescence —
cell has a limited
number of divisions
•Growth Regulating
Proteins
•Contact
Inhibition
–Stop dividing
when touching
another cell
Copyright 2005—Brooks/Cole—Thomson Learning
Tobin and Dusheck: Asking About Life, 3E
Chapter 8
When Is It Time to Divide?
•Divide only when cell has doubled
its mass
•Various events regulate a cell’
s
passage through the cell cycle,
including the completion of DNA
synthesis and fluctuations in
cyclins (proteins whose
concentrations change during the
cell cycle)
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Tobin and Dusheck: Asking About Life, 3E
Chapter 8
Key Concepts
•Cell division involves 3 processes:
replication of DNA, its equal
distribution to each daughter cell,
and division of cytoplasm
•Microtubules and other components
provide for chromosomal distribution
•Similar molecular mechanisms are
used to regulate the cell cycle in all
eukaryotic cells
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