Transcript Cell Growth & Division Notes

Chapter 10
Cell Growth & Division
Cell Division
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There are 2 main reasons cell divides:
1.
2.
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The cell has more trouble trying to move
nutrients and wastes across the cell
membrane.
The larger a cell becomes, the more
demands it puts on its DNA.
Bottom line – cells need to be replaced
Cell Cycle
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The sequence of
growth and division of
a cell
An average cycle may
be 22 hours
Two general periods:
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1. growth phase
2. division phase
Interphase (Growth phase)
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Most of the cell’s
life is spent in
interphase
Longest phase –
(90% of cell’s
growth)
Centrioles – help to
organize cell division
Chromatin – DNA bound
protein within the nucleus
Interphase (Growth phase)
New DNA is formed
during 3 phases:
G1 – 1st period of growth
1. Increase in size.
2. Makes new proteins and
organelles.
S1 – DNA is synthesized or
replicated
1. Chromosomes are replicated.
2. New DNA molecules are
made.
G2 – final cell growth
1. Shortest phase
2. Prepares cell for mitosis
Terms to know
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Chromosome –
contains genetic
information (DNA)
passed from one
generation to the next
Spindle – microtubule
that helps separate
chromosomes
A – centromere:
center of chromosome
B – chromatids: two
identical “sister” parts
of the chromosome
Mitosis (Division phase)
4 phases:
(PMAT)
1)
2)
3)
4)
Prophase
Metaphase
Anaphase
Telophase
Mitosis
Takes place within the nucleus of the cell
4 phases that blend from one to another
Prophase
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1st and longest phase
of mitosis
Chromatin become
chromosomes
Chromatids are joined
by centromere
Nucleus disappears
Centrioles migrate to
poles
Spindles are formed
Metaphase
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2nd phase of mitosis
Chromosomes meet
in the middle of cell
Pulled by spindles
Each chromosome is
attached to top of
spindle
Anaphase
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3rd phase of mitosis
Centromeres are split
apart
Chromatids are pulled
apart and begin to
drift to opposite poles
Telophase
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Final phase of mitosis
Begins when chromatids
reach poles
New nucleus starts to
form
Chromosomes start to
unwind
Spindles disappear
Cytoplasm begins to
divide
Cytokinesis
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Cytoplasm
pinches in
half
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Each daughter cell has
an identical set of
chromosomes
Plants
apical
meristem
Rat – epithelial cells
Prophase, Metaphase, Anaphase,
or Telophase?