Transcript Caylor 102 Biology Unit 3

Chapter 9.1 and 9.2
Cellular Growth and Mitosis notes
Why does a cell divide?
• As the cell gets larger, the surface area to
volume ratio gets smaller
• There are too many demands placed on
the nucleus(specifically the DNA)
• Too much difficulty moving things across
the cell membrane
• It takes too long for signaling proteins to
travel the entire distance of the cell
The Cell Cycle
http://www.scq.ubc.ca/wp-content/cellcycle.gif
Interphase
•
•
•
•
•
Most of a cell’s life is spent in Interphase
Coined G1, S, and G2
The cell grows during G1
DNA is replicated (synthesis) during S
The cell prepares for mitosis during G2
• Mitosis is the division
of cells producing two
cells with the same
number of
chromosomes
Prophase
• Longest phase of mitosis
• Chromatin coils into
chromosomes
• Nuclear envelope
disappears
• Centrioles form and move
to opposite poles of cell
• Spindle fibers form from
centrioles and begins to
cross cell
Metaphase
• Chromosomes line up
in the middle of the
cell
• Spindle now forms
across the cell
Anaphase
• Spindle fibers begin
to shorten
• Chromosomes are
pulled apart
• Now the chromosome
halves are referred to
as chromatids
Telophase
• Chromatids reach
poles
• Chromosomes
unwind into chromatin
• Spindle fibers break
down
• Nucleolus and nuclei
reform
• Plasma membrane
begins to pinch in
Cytokinesis
• Division of cytoplasm
• In animal cells: cell
membrane continues to
pinch in until two cells are
formed
• In plant cells: cell plate
forms in center of cell and
eventually splits cells
• At the end of mitosis, two
new cells are produced;
called “daughter” cells
Quiz 5
a.
b.
c.
1.
2.
3.
4.
5.
6.
7.
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Anaphase d. metaphase g. telophase
Chromatin e. mitosis
Interphase f. prophase
In _______ the chromosomes are split apart.
Chromosomes are made up of _____________.
In _______________ the nucleolus disappears and the nuclear
membrane disintegrates.
In _____________ the chromosomes reach the poles and the cell
divides
__________________ is the growth phase of the cell cycle.
In ? the chromosomes line up in the middle of the cell.
?? Is how cells reproduce.