Transcript Mitosis and the Cell Cycle

Cell Division
Slide # 2
Why Cells Make More Cells
1. Most cells go through a series of changes in order
to maintain homeostasis.
2. Cells need to reproduce (divide) when their surface area
can no longer supply the much larger volume with
nutrients and get rid of wastes.
Surface Area
(length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area
to Volume
Slide # 3
Introduction to Mitosis
1. Two main stages of cell division
a. Mitosis: division of the nucleus
b. Cytokinesis: division of the
cytoplasm
2. Produces 2 cells called daughter
cells
a. Cells are genetically identical
3. Mitosis is source of new cells for
a. Growth
b. Development
c. Repair
d. Replacement of old cells
Normal red blood cells
only live for 120 days.
Then they die & stem
cells make new ones.
Slide # 4
Chromosomes
1. Chromosomes: made up
of DNA & proteins
2. Carry the cell’s coded genetic
information
3. Different organisms have a
different number of
chromosomes
Fruit flies have 8
chromosomes in each
body cell
Humans have 46
chromosomes in
each body cell
Frogs have 26 chromosomes
in each body cell
Slide # 5
Vocabulary
1. Chromatin: the relaxed, uncoiled
state of the chromosome
2. Chromatid: one of two identical
“sister” parts of a duplicated
chromosome
3. Chromosome: threadlike
structures within the nucleus
containing genetic information
that is passed on from generation
to generation
4. Centromere: chromosome region
that joins 2 sister chromatids
Slide # 6
Cell Cycle
1. Cell cycle: Sequence of events between the time a cell
divides to form 2 daughter cells & the time those 2 cells
divide
2. Consists of 2 phases
– M phase: Mitosis
& Cytokinesis
– Interphase
– G1
– S
– G2
Mitosis Discovered
Slide # 7
Walther Flemming first discovered
mitosis in 1870 and reported is
discovery of chromosomes and
mitosis in 1882.
Metaphase in a salamander cell
drawn by Walther Flemming
from a stained slide.
Slide # 8
Interphase: 3 Phases
1. G1 phase: Growth Phase
a. Cell performs all life’s activities:
protein synthesis, waste removal,
organelle synthesis, etc.
2. S phase: DNA Replication
a. DNA makes a copy of itself
b. Produces 2 identical sets of
chromosomes
3. G2 phase: Preparation
a. Cell produces centrioles & spindle
fibers needed to move the
chromosomes
centrioles
Nucleus &
duplicated
chromosomes
Slide # 9
Mitosis
1. Described as movement of
chromosomes
2. Continuous series of events
3. Divided into four phases so
that it is easier to understand
Cell Cycle
Slide # 10
Prophase: 1st Phase
1. Chromatin (DNA) condenses,
coils, & becomes rod shaped
2. Centrioles move to opposite
ends of cell
3. Spindle fibers attach to
chromosomes
4. Nuclear membrane breaks
down
Slide# 11
Metaphase
1. Spindle fibers push & pull
chromosomes until they
line up across center of
cell
2. Centromere of each
chromosome pair is
attached to a spindle fiber
Slide # 12
Anaphase
1. Spindle fibers shorten &
paired chromatids separate
2. Spindle fibers pull
separated chromosomes to
opposite ends of the cell
3. Centromere of each pair
divides; now have
individual chromosomes
Slide 13
Telophase
1. Chromosomes begin to
uncoil and de –
condense
2. Nuclear membrane
reforms around each
new set of
chromosomes
Slide # 14
Cytokinesis
1. Cytokinesis is division of the
cytoplasm
2. Distributes the organelles
a. In animal cells, the cell membrane
pinches together around the
middle of the cell and forms 2
cells.
b. In plant cells, a cell plate forms
across the middle of the cell and
new cell walls form between the
daughter cells
Slide # 15
Cancer Cells
1. Normal cells contain check points to regulate
the cell cycle, & stop at appropriate check points.
2. Cancerous cells do not respond to check points
and continue rapidly through the cell cycle. This
results in masses of undefined cells called tumors.
3. Cancer cells do not mature; they become more
immature.
Binary Fission
1. Binary fission is the process
by which all bacteria
reproduce .
2. Each resulting daughter cell is
genetically identical to the
parent cell.
3. Under ideal conditions,
bacteria can reproduce once
every 20 minutes
If you start out with 1 bacterium cell,
how many could be produced after 7
hours?
2, 097, 152 produced in just 7 hours!