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Nematoda Secernenta in Anaphase Contributed by Richard J.
Harris courtesy of BIODIDAC
1.
2.
Mitosis- division of the cell nucleus
Cytokinesis- division of the cytoplasm
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SEM image of
Chromosomes
I.
1.
Chromosomes- contain DNA (genetic info) which is passed
from parent to offspring.
2.
Before a cell divides each chromosome is copied
3.
Structure of the chromosome:
* Two sister chromatids; are identical
* Centromere- holds the sister chromatids together resulting in an
x-shaped c’some
Sister chromatids
Centromere
* When the cell divides, the chromatids separate.
* Each new cell gets one chromatid.
Cell division Micrograph
II.
1.
Cell Cycle- the series of events that takes place in a cell
leading to its division & replication
2.
During the cell cycle:
* a cell grows
* prepares for division
3.
Divides to form two daughter cells, each of which begins
the cycle again
4. The cell cycle consists of four phases:
*G1 (First Gap Phase)
*S Phase (Synthesis)
*G2 (Second Gap Phase)
*M Phase (Mitosis)
III.
1.
Interphase- the first
stage of the cell cycle.
During this phase the
cell:
* Grows
* Makes new proteins &
organelles
* C’somes are replicated
* DNA is made
2.
Interphase has 3 phases:
G1, S, & G2
3.
During G1, the cell:
* increases in size
* synthesizes new proteins and organelles
4.
During the S phase:
* chromosomes are replicated
* DNA synthesis takes place
5.
Once a cell enters the S phase, it usually completes the
rest of the cell cycle
6.
The G2 Phase (Second Gap Phase)
* organelles & molecules required for cell division are produced
* Once G2 is complete, the cell is ready to start the M phase—
Mitosis
IV.
1. Mitosis has 4 phases:
*Prophase
*Metaphase
*Anaphase
*Telophase
2.
Centrioles- barrel shaped structures that are made of
groupings of microtubules
3.
Spindle- a fanlike microtubule structure that helps
separate the chromosomes.
4.
Chromatin- a combination of DNA and proteins that make
up c’somes
5. Prophase
*The 1st & longest phase
of mitosis
*The centrioles separate &
end up on opposite sides of
the nucleus in an area
called the centromere
A cell in prophase of mitosis. (An epithelial cell in prophase of mit
treated with the anti-cancer drug taxol. Chromosomes are labeled
Taricha granulosa (newt) lung.)
*Chromatin condenses into
chromosomes.
*The nuclear envelope
breaks down.
Observing Mitosis with Fluorescence Microscopy. Prophase.
© 1995-2013 by Michael W. Davidson and The Florida State University.
6. Metaphase
*2nd phase of mitosis
*The chromosomes
line up across the
center of the cell
*Microtubules
connect the
centromere of each
chromosome to the
poles of the
spindle.
Observing Mitosis with Fluorescence Microscopy. Metaphase.
© 1995-2013 by Michael W. Davidson and The Florida State University.
7. Anaphase
*3rd phase of mitosis
*the duplicated
centromeres of each
pair of sister
chromatids separate
*the now-daughter
chromosomes begin
moving toward
opposite poles until
they have separated
into two groups.
Observing Mitosis with Fluorescence Microscopy. Anaphase.
© 1995-2013 by Michael W. Davidson and The Florida State University
8. Telophase
*The last phase of
mitosis
*Chromosomes
gather at opposite
ends of the cell
*A new nuclear
envelope forms
around each
bunch of
chromosomes.
Observing Mitosis with Fluorescence Microscopy. Telophase.
© 1995-2013 by Michael W. Davidson and The Florida State Universi
9. Cytokinesis
*the cytoplasm
pinches in half.
*Each daughter
cell has an
identical set of
duplicate
chromosomes.
Actin (blue) and microtubules (orange) at the end of cytokinesis in a gr
urchin zygote. University of Washington Center for Cell Dynamics
10.
*structure known as
the cell plate forms
midway between the
divided nuclei
*The cell plate
gradually develops
into a separating
membrane.
*A cell wall then
begins to appear in
the cell plate.
Cell plate
Cell wall
11.
*A cleavage furrow
forms-An indention
formed by
microfilaments
*The pulling of the
filaments
separates the
cytoplasm of the
daughter cells
12.
*95% of the cell cycle is
spent in interphase
*A typical rapidly dividing
human cell with a total
cycle time of 24 hours:
*the G1 phase might
last about 11 hours
*S phase about 8 hours
*G2 about 4 hours
*and M about 1 hour.
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*Page 249 “Analyzing DataThe Life Span of Human
Cells”
*Read the paragraph and
answer questions 1-4
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