Ch. 12: The Cell Cycle
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KEY CONCEPTS
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Cell division results in genetically
identical daughter cells
The mitotic phase alternates with
interphase in the cell cycle
The eukaryotic cell cycle is regulated by
a molecular control system
Key Roles of Cell Division
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Reproduce more of your own kind
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Produce eggs and sperm, pollen, spores
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Larger organisms (toddler to teen)
Renewal
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Meiosis is a form of cell division
Growth
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R.Virchow in 1855 “Omnis cellula e cellula”
(Every cell comes from a cell)
Amoeba or plant cuttings
Physically pass a copy of the ‘information’ on
to the next generation
Replace shed skin cells
Repair
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Fix a wound
Genetically Identical Daughter Cells
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Copying of genetic material
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Equal distribution of genetic material
copies
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Accuracy generation after generation
Precision – with no dilution
Even distribution of cytoplasm and
membrane
Physical separation of the two new cells
Each cell is half of the parent, parent
doesn’t exist as an individual anymore,
yet isn’t gone……
Chromosome Redistribution
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Genome entire genetic information for
an individual or species
Chromosomes manageable packages of
DNA
Somatic cells  body cells, contain a set
number of chromosomes for their
species; humans 23 pairs (46)
Gametes  reproductive cells like egg
and sperm that have only 1 of each
chromosome; humans one set of 23
Chromatincomplex of protein and DNA
that is very long and linear
More terminology
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Sister chromatids  duplicated
chromosomes, identical
information, initially attached
to each other
Centromere waist region of
chromatid (arm and cohesions)
Mitosis  division of a
eukaryotic nucleus
Cytokinesis  division of the
cytoplasm
Meiosis  process that
generates gametes
The Cell Cycle
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Interphase
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Mitotic Phase - “mitosis”
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G1 – normal growth (originally “gap”)
S – synthesis of DNA; replication of
chromosomes
G2 – extra proteins and cytoplasmic organelles
like mitochondria
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
division of the nucleus
- physical division of the cytoplasm
Phases of mitosis
Details of Phases
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Interphase
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G1- gap one, not much visible, cell is
growing, normal- everyday life,
accessing DNA, making proteins
S – synthesis of new DNA, all or
nothing event, replication of
chromosomes in entirety
G2 – now ready to divide nucleus,
produce new structures for after
division like ER and mitochondria
Details of phases
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Mitosis
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Prophase – chromatin is chromosomes, visible
structure, packaged format
Prometaphase – centrosomes move apart,
spindle forms, spindles attach to kinetochores,
tug-o-war
Metaphase- phase where chromosmes are
aligned at equator
Anaphase – chromosomes are in motion, sister
chromatids are separate
Telophase – 2 separate nuclei, return to
chromatin
Details of phases
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Cytokinesis
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Still part of mitosis (Interphase +
Mitosis = Cell Cycle)
This is division of cytoplasm, as
opposed to division of the nucleus
Overlaps with both interphase and
telophase (see pg 231)
Plant vs Animal
Binary fission
Mitosis, binary fission and in between
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Binary fission =
prokaryotes
 One chromosome
 No nuclear
membrane
 Less to organize
Mitosis = eukaryotes
 Multiple
chromosomes
 Nuclear membrane
 Organelles to
organize
Regulation of the cell cycle
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Cytoplasmic (chemical) regulation
Mechanical (physical) regulation
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Separate PPT
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Lack of regulation in the cell cycle
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Cells which don’t respond to check point
signals within the cell or to physical
conditions like contact tend to divide out
of control and are called cancer cells.
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Own blood supply
Use lots of nutrients
Transformation turns normal cell into cancer
cell
(related to microtubles, genetic? environmental? )
Mass of extra cells is tumor (benign)
Malignant tumors invade other tissues and
organs
Spreading of cancer cells is called metastasis