Download PowerPoint Chp 9

Cell Division and Mitosis
Starr/Taggart’s
Biology:
The Unity and Diversity of Life,
Chapter 9
9e
Key Concepts:
Continuity of life depends on reproduction
After cell division, each daughter cell must
receive the same amount of DNA
The cell cycle: Interphase and Mitosis
DNA and proteins make up chromosomes
in eukaryotic cells
Members of the same species have the
same number of chromosomes in their
cells
Key Concepts:
The body cells of many organisms have a
diploid chromosome number
Mitosis keeps the chromosome number
constant
Mitosis is the basis of growth and tissue
repair in multicelled eukaryotes.
Single-celled eukaryotes and many
multicelled eukaryotes reproduce by
mitosis
Overview
DNA contains hereditary instructions
Before cells reproduce, they must undergo
nuclear division
Mitosis
Meiosis
Multicelled organisms grow and repair
themselves by mitosis
Overview
Mitosis and meiosis are nuclear division
mechanisms
Mitosis in somatic cells allows growth,
repair, and asexual reproduction
Meiosis occurs in germ cells, produces
gametes, allows sexual reproduction
Prokaryotic cells reproduce asexually
Chromosomes
Each chromosome duplicates in
preparation for mitosis
Sister chromatids remain attached
Mitosis and Chromosome
Number
Chromosome number = Total of
chromosomes in somatic cells
Humans 46
Gorillas 48
Pea plants 14
Chromosomes are in pairs
Humans 23 pairs
2n “diploid”
1n “haploid” (gametes)
The Cell Cycle
A diploid cell produces two diploid
daughter cells
Two phases in cell cycle
Interphase
Longest phase
Increase in mass, doubles components, and
duplicates DNA
Mitosis
Nuclear division
Interphase
G1
“Gap” - cell growth before DNA
replication
S
“Synthesis” - DNA replication
G2
“Second Gap” - preparation for division
The length of each part differs among
different cell types
The Cell Cycle
Mitosis
Four stages
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Cytoplasmic division
Prophase
 Chromosomes become visible
 Spindle apparatus forms
Centrioles move apart to opposite poles
Microtubules break apart into tubulin
subunits
New tubulin subunits form the spindle
Nuclear envelope breaks up
Prophase
Metaphase
Chromosomes interact with microtubules
on spindle apparatus
Attachment at centromeres
• Kinetochore
Tubules pull on chromosomes
Orientation of sister chromatids to
opposite poles
Alignment of chromosomes midway
between the poles
Metaphase
Anaphase
Separation of
sister chromatids
Movement toward
opposite poles
Separation of Sister
Chromatids
Microtubules attached to centromeres
shorten and pull chromosomes towards
poles
Separation of Sister
Chromatids
Spindle elongates and the spindle poles
are pushed farther apart by overlapping
microtubules
Telophase
Chromosomes arrive at spindle poles
Chromosomes return to threadlike forms
New nuclear membranes form
Two nuclei form
Cytokinesis
Division of cytoplasm
Forms two cells
Metaphase to Interphase
Cytoplasmic Division
Cytokinesis
Between late anaphase and end of
telophase
In plants: cell plate forms
Vesicles fuse
In animals: cleavage
Cleavage furrow - depression forms at cell’s
midsection
In Conclusion
 A parent cell provides each daughter cell
with hereditary instructions
 Eukaryotes divide by mitosis or meiosis
and prokaryotes divide by binary fission
 Each chromosome is one DNA molecule
with proteins attached
 Cells with a diploid number (2n) contain
two of each kind of chromosome
In Conclusion
 Mitosis maintains the chromosome number
from one cell generation to the next
 Mitosis is the basis of growth and tissue
repair, and asexual reproduction in some
eukaryotes
 The cell cycle includes interphase and
mitosis
 The phases of mitosis are prophase,
metaphase, anaphase, and telophase

developed by M. Roig