September 11, 2015
 TO DO: Notebook, pencil/pen.
 WARM UP: How do you think cells make
more cells?
HOMEWORK:
 www.biohs.weebly.com
Phases
of
the
Cell
Cycle
 The cell cycle consists of
 Interphase – normal cell activity
 The mitotic phase – cell divsion
INTERPHASE
Growth
G1
(DNA synthesis)
Growth
G2
Functions of Cell Division
100 µm
(a) Reproduction. An amoeba,
a single-celled eukaryote, is
dividing into two cells. Each
new cell will be an individual
organism (LM).
200 µm
20 µm
(b) Growth and development.
(c) Tissue renewal. These dividing
This micrograph shows a
bone marrow cells (arrow) will
sand dollar embryo shortly after
give rise to new blood cells (LM).
the fertilized egg divided, forming
two cells (LM).
Chromosomes
 A diploid cell has two sets of each of its chromosomes
 A human has 46 chromosomes (2n = 46)
 In a cell in which DNA synthesis has occurred all the chromosomes are
duplicated and thus each consists of two identical sister chromatids
Maternal set of
chromosomes (n = 3)
2n = 6
Paternal set of
chromosomes (n = 3)
Two sister chromatids
of one replicated
chromosome
Centromere
Two nonsister
chromatids in
a homologous pair
Pair of homologous
chromosomes
(one from each set)
Phases of the Cell Cycle
 Interphase
 G1 - primary growth
 S - genome replicated
 G2 - secondary growth
 M - mitosis
 C - cytokinesis
Interphase
occurs before mitosis begins
• Chromosomes are copied (# doubles)
• Chromosomes appear as threadlike coils
(chromatin) at the start, but each chromosome
and its copy(sister chromosome) change to sister
chromatids at end of this phase
Nucleus
CELL
MEMBRANE
Cytoplasm
Interphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase
1st step in Mitosis
• Mitosis begins (cell begins to divide)
• Centrioles (or poles) appear and begin to move to
opposite end of the cell.
• Spindle fibers form between the poles.
Centrioles
Sister chromatids
Spindle fibers
Prophase
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
2nd step in Mitosis
• Chromatids (or pairs of chromosomes) attach to the
spindle fibers.
Centrioles
Spindle fibers
Metaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase
3rd step
in Mitosis
• Chromatids (or pairs of chromosomes) separate and
begin to move to opposite ends of the cell.
Centrioles
Spindle fibers
Anaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase
4th step
in Mitosis
• Two new nuclei form.
• Chromosomes appear as chromatin (threads rather than
rods).
• Mitosis ends.
Nuclei
Chromatin
Nuclei
Telophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis
occurs after mitosis
• Cell membrane moves inward to create two daughter
cells – each with its own nucleus with identical
chromosomes.
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Plant Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Cell Cycle
19
- Cell Division
The Cell Cycle
20
20
Cell Division
 An integral part of the cell cycle
 Results in genetically identical daughter cells
 Cells duplicate their genetic material
 Before they divide, ensuring that each daughter
cell receives an exact copy of the genetic
material, DNA