Transcript A View of Life

The Cell Cycle and Cellular Reproduction
Chapter 9
Mader: Biology 8th Ed.
Outline
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Interphase
Mitotic Stage
Cell Cycle Control
Apoptosis
Mitosis
Mitosis in Animal Cells
Cytokinesis
Cancer
Prokaryotic Cell Division
Mader: Biology 8th Ed.
Interphase
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Most of the cell cycle is spent in interphase.
– G1 - Cell doubles its organelles and
accumulates materials needed for DNA
synthesis.
– S - DNA replication.
– G2 - Cell synthesizes proteins necessary
for cell division.
Mader: Biology 8th Ed.
Mitotic Stage
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Cell division stage that includes mitosis
(nuclear division) and cytokinesis
(cytoplasm division).
Mader: Biology 8th Ed.
Cell Cycle
Mader: Biology 8th Ed.
Cell Cycle Control
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Researchers have identified internal signal
protein (cyclin) that increases and
decreases as cell cycle continues.
– Must be present for the cell to proceed
from the G2 stage to the M stage and from
G1 stage to S stage.
 Allows time for any damage to be
repaired.
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Cell Cycle Control
Mader: Biology 8th Ed.
Apoptosis
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Often defined as programmed cell death.
– Cells routinely harbor enzymes
(caspases) necessary for apoptosis to
occur.
 Ordinarily held in check by inhibitors,
but can be unleashed by internal or
external signals.
Mitosis increases and apoptosis decreases
the number of somatic cells.
Mader: Biology 8th Ed.
Apoptosis
Mader: Biology 8th Ed.
Mitosis
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When a eukaryotic cell is not undergoing
division, the DNA within the nucleus is a
tangled mass of chromatin.
– Condenses into chromosomes
 Each species has a characteristic
number of chromosomes.
 Diploid (2n) - Two of each kind.
 Haploid (1n) - One of each kind.
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Mitosis
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During mitosis, a diploid nucleus divides to
produce diploid daughter nuclei.
– Two identical chromatids are called sister
chromatids.
 Attached to each other at centromere.
 During nuclear division, sister
chromatids separate at the
centromeres, and each duplicated
chromosome gives rise to two
daughter chromosomes.
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Duplicated Chromosomes
Mader: Biology 8th Ed.
Mitosis in Animal Cells
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Each centromere in an animal cell contains
a pair of barrel-shaped organelles
(centrioles) and an array of short
microtubules (aster).
– Centromeres organize mitotic spindle,
which contains many fibers, each
composed of a microtubule bundle.
Mader: Biology 8th Ed.
Mitosis in Animal Cells
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Prophase
– Chromatin has condensed.
– Nucleolus disappears.
– Nuclear envelope disintegrates.
– Spindle begins to assemble.
Prometaphase
– Kinetochores develop on centromere.
 Attach sister chromatids to spindle fibers.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mitosis in Animal Cells
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Metaphase
– Chromosomes, attached to kinetochore
fibers, are in alignment at center of cell.
Anaphase
– Sister chromatids split, producing daughter
chromosomes.
 Daughter chromosomes are pulled to
opposite poles.
Mader: Biology 8th Ed.
Mitosis in Animal Cells
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Telophase
– Spindle disappears as new nuclear
envelopes form around the daughter
chromosomes.
 Chromosomes become diffuse chromatin
again.
 Nucleolus appears in each daughter
nucleus.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Plant Cell Division
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Meristematic plant tissue retains the ability
to divide throughout the plant’s life.
– Found at root and shoot tips.
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Phases of Mitosis in Plant Cells
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Cytokinesis
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Cytokinesis accompanies mitosis in most
cells, but not all.
– Mitosis without cytokinesis results in a
multinucleated cell.
 Begins in anaphase, continues in
telophase, but does not reach
completion until the following interphase
begins.
Mader: Biology 8th Ed.
Cytokinesis
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Animal Cells
– Cleavage furrow, membrane indentation
between daughter nuclei, begins as
anaphase nears completion.
 Deepens when a band of actin
filaments (contractile ring) forms a
circular constriction between the two
daughter cells.
Mader: Biology 8th Ed.
Cytokinesis in Animal Cells
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Cytokinesis
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Plant Cells
– Rigid cell wall surrounding plant cells
does not permit cytokinesis by furrowing.
 Begins with formation of a cell plate
which eventually becomes new plasma
membrane between the daughter cells.
Mader: Biology 8th Ed.
Cytokinesis in Plant Cells
Mader: Biology 8th Ed.
The Cell Cycle and Cancer
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Cancer is a growth disorder that results from
the mutation of genes regulating the cell
cycle.
– Carcinogenesis, development of cancer,
tends to be gradual.
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Characteristics of Cancer Cells
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Lack differentiation.
Have abnormal nuclei.
Form tumors.
– Loss of contact inhibition.
Undergo metastasis.
– New tumors distant from primary tumor.
Undergo angiogenesis.
– Formation of new blood vessels.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Origin of Cancer
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Mutations in DNA repair mechanisms.
Mutations to proto-oncogenes and tumorsuppressor genes.
– Proto-oncogenes become oncogenes.
Telomerase allows cancer cells to
continually divide.
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Prokaryotic Cell Division
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Asexual Reproduction - offspring are
genetically identical to the parent.
– Binary fission produces two (binary)
daughter cells that are identical to the
original parent.
 Prokaryotes contain a single
chromosome with only a few proteins.
Mader: Biology 8th Ed.
Binary Fission
Mader: Biology 8th Ed.
Review
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Interphase
Mitotic Stage
Cell Cycle Control
Apoptosis
Mitosis
Mitosis in Animal Cells
Cytokinesis
Cancer
Prokaryotic Cell Division
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.