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CELL GROWTH
& DIVISION
Why do cells divide?
DNA OVERLOAD
1. _____________________
As cell grows bigger demand on DNA
“genetic library” becomes too great
Material exchange can’t keep up
2. _____________________
As cell grows bigger demand for
transport across membrane is too
great
Ability to transport of oxygen,
food, waste across cell membrane
depends on _______________
SURFACE AREA
Need for these depends on
___________
CELL VOLUME
As cell grows these DON’T increase at the
same rate
BIGGER CELLS NEED MORE FOOD
and OXYGEN, but CAN’T TRANSPORT
IT FAST ENOUGH or IN BIG
ENOUGH QUANTITIES!
http://www.animationlibrary.com
Multicellular organisms grow
mainly by increasing cell number
DNA CAN BE:
SPREAD OUT IN
NON-DIVIDING
CELLS
CHROMATIN
SCRUNCHED UP
IN DIVIDING
CELLS
CHROMOSOMES
DNA in PROKARYOTES
• BACTERIAL
DNA is
CIRCULAR
• HAVE ONE
CHROMOSOME
• NO NUCLEUS
DNA in PROKARYOTES
• Plasmids are small circular DNA
molecules
– Help bacteria to survive stress
– Antibiotic resistance
• Recombinant DNA technology
– Insulin:
http://www.abpischools.org.uk/page/modules/di
abetes/diabetes6.cfm?coSiteNavigation_allTopic
=1
DNA in EUKARYOTES
• DNA is RODSHAPED
CHROMOSOMES
• MANY PAIRS
• FOUND IN
NUCLEUS
• DNA in one human
cell would be about 6
feet long if it were
all stretched out
(Karyotype)
DNA in EUKARYOTES
• Diploid
• When a (somatic) cell
contains two sets of
chromosomes
• Humans: 2n=46
• Haploid
• When a (gamete) cell
contains one set of
chromosomes
• Humans: n=23
• Zygote
• Fertilized egg cell
(Karyotype)
Chromosome structure
• Telomere
– A region of repetitive
nucleotide sequences
– Protects the end of the
chromosome from
deterioration or from
fusion with neighboring
chromosomes
– Telomerase replaces
telomeres
– Shortens each time a cell
divides
– Associated with aging and
cancer
Chromosome structure
• ______________
CHROMATIDS
2 identical arms
• _____________
CENTROMERE
constricted area
holds chromatids
together
HOMOLOGOUS
•__________________
PAIR
2 of each chromosome
(one from mom; one from dad)
HOMOLOGOUS CHROMOSOMES
• SAME SIZE
• SAME SHAPE
• CARRY GENES for the
SAME TRAITS
IDENTICAL
• BUT NOT
______________!
(Don’t have to have the
SAME CHOICES)
http://arnica.csustan.edu/biol3020/cell_division/cell_division.htm
CELL DIVISION in PROKARYOTES
Bacteria reproduce using
BINARY FISSION
__________________________________
http://fig.cox.miami.edu/~cmallery/150/mitosis/fission.jpg
CELL CYCLE
INTERPHASE – non-dividing phase
G1- Grow bigger
Cell is “doing its job”
DNA is spread out as chromatin
S - Synthesis (copy DNA)
& chromosomal proteins
G2- Grow bigger, make organelles &
molecules needed for cell division
CELL DIVISION
MITOSIS – Nuclear division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis – Cytoplasm divides
G0 – cell stops dividing
(Ex: nerve cell)
INTERPHASE (G1 - S - G2)
•In between divisions
•Cells are in this phase most of the
time
•Can see nucleus
•DNA spread out as chromatin
Can’t see chromosomes
DNA gets copied (S)
Cell gets ready to divide
PROPHASE
1st dividing phase
•DNA scrunches into chromosomes
•Centrioles appear in centrosome region
& move to poles
•Nuclear membrane & nucleolus disappear
•Spindle fibers form & attach to
chromosomes
CENTROSOME
________
region organizes spindle
Spindle MICROTUBULES are part of cytoskeleton
METAPHASE
Chromosomes line up in
middle
___________
ANAPHASE
Centromeres split
apart
Centrioles pull chromatids_______
TELOPHASE (reverse prophase steps)
two nuclei
See ______
Nuclear membrane & nucleolus return
Chromosomes spread out as chromatin
Centrioles disappear
Spindle fibers disappear
CYTOKINESIS
Cytoplasm splits into 2 cells
ANIMAL CELLS pinch cytoplasm in two
with a ______________________
CLEAVAGE FURROW
CYTOKINESIS
Cytoplasm splits into 2 cells
PLANT CELLS can’t pinch because
they have a sturdy ____________
CELL WALL
Plant cells separate cytoplasm by
CELL PLATE
growing a _______________
down the middle.
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Go to
Section:
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Cell Cycle
includes
G1 phase
Interphase
M phase
(Mitosis)
is divided into
is divided into
S phase
G2 phase
Prophase
Metaphase
Anaphase
Telophase
Outline Mitosis
http://www.uic.edu/classes/bios/bios10
0/lecturesf04am/lect16.htm