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Cell cycle and
Reproduction
BIO…
LIFE….
THINK ABOUT THIS:
What do we do in our lifetime?
What are the major stages of our life?
What are the Major stages of
physical development in our lives?
 What would it look like
if we put this into a pie
chart?
 Cell cycle: repeating sequence of cellular
growth and division during the life of an
organism; check points trigger the next
stage of the cycle
The life of a cell
 Cells have a life cycle just like we do- born, grow, reproduce,
and die.
 They only spend part of
their life cycle reproducing (M)- mitosis
Imagine you are a bacteria:
What are the major stages in your
life?
TRY ME:
 What is A? B? C?
 What is D/E/F/G collectively
called?
 What is D?
 What is E?
 What is F?
 What is G?
https://www.youtube.com/watch?v=65SODTL
_QsA
Figure 9-8 The eukaryotic cell cycle
G1: cell growth and
differentiation
G2: cell
growth
and
preparation
for cell
division
S: synthesis
of DNA;
duplication of
chromosomes
Cell Cycle
1. Interphase (G1, S, G2) – cell grows,
prepares to divide (G phases) and DNA
replicates (S phase)
2. Mitosis: nucleus divides; each nuclei
winds up with the same # and kind of
chromosomes as the parent (P-M-A-T)
3. Cytokinesis: division of cytoplasm
WHY DO CELLS DIVIDE?
WHY DO THEY DO MITOSIS???
 UNICELLULAR vs. MULTICELLULAR?
Why do cells divide?
 UNICELLULAR
 To reproduce (asexual reproduction)- budding/binary fission
 Ex. Bacteria
 hydra
 vs. MULTICELLULAR?
 Grow
 Repair/replace cells that have been lost or damaged
Let’s think a second:
THINK: Why do we have cycles and cells split? Why doesn’t
the cell just get bigger and bigger?
Neither!!!
Which turtle
has bigger
cells?
Their cells are the
same size… this one
just has MORE!
Why don’t cells continue to grow?
There are two main reason why cells divide instead of continue
to grow:
1. The larger the cell becomes, the more demands the cell
places on its DNA
2. The cell has more trouble moving enough nutrients and
wastes across the cell membrane.
DNA “Overload”
 Information that controls a cell’s function is stored in a
molecule knows as DNA
 In eukaryotic cells, DNA is found in the nucleus
DNA “Overload”
 When a cell is small, the information stored in the DNA is
able to meet all of the cell’s needs
 If a cell was too large an “information crisis” would occur and
the cell would not function properly
Example: Small library in a large
city
Exchanging Materials
 Food, water and nutrients enter the cell through its cell
membrane
 Waste products leave in the same way
Exchanging Materials
Example: Small streets in a big town
Exchanging Materials
 The relationship between a cell’s volume and its surface
area is the key to understanding why cells must divide as
they grow!
Ratio of Surface Area to Volume
Ratio of Surface Area to Volume
 The volume increases much faster than the surface area, causing
the ratio of surface area to volume to decrease.
 This decrease creates serious problems for the cell.
Formula for calculating ratio:
Ratio = Surface Area/Volume
SPLIT GROUPS: FIND SA , Volume
and ratios for
3x3, 5x5, 8x8, 10x10
Lab surface/volume ratio
CAN WE FIND THIS EXPERIMENTALLY???
FIND SA , Volume and ratios for
For: 3x3, 5x5, 8x8, 10x10
Problem: What happens to the surface/volume ratio when a
cube gets really big?
Hypothesis:
Methods:
Result table in excel:
Conclusion:
So what happens when cells get
TOO LARGE????
 THEY SPLIT- MITOSIS.
DNA replicates in
interphase?
Which part of cell
cycle???
What happens in
each:
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html#
no cell wall
cell wall
Mitosis
parent
cell
46
chromosomes
92
chromosomes
46
chromosom
es
daughter
cells
46
chromosom
es
AMEOBA SISTERS:
https://www.youtube.com/watch?v=gwcwSZIf
KlM&list=PLwL0Myd7Dk1F1ppDaLx3ygO_7xA-yyd4&index=3
BUT WHY CELLS DON’T JUST SPLIT ALL THE TIME????
Or in other words….
What happens if things go
wrong with checkpoints?
THINK ABOUT THIS!!!!
 Loss of Control of the Cell Cycle
 If checkpoints are not working properly,
the cell cycle can cause the cell to grow
uncontrollably
 leads
to cancer .
THINKING QUESTION:
What biomolecule controls checkpoints?
AMEOBA SISTERS:
https://www.youtube.com/watch?v=lpAa4TWjHQ4&list=PLwL0Myd7Dk1F1ppDaLx3ygO_7xA-yyd4&index=2
And what controls the making of proteins? DNA
SO WHAT’S THE DIFFERENCE BETWEEN
PROKARYOTIC AND EUKARYOTIC DNA
How Is the DNA in Eukaryotic
Chromosomes Organized?

Eukaryotic chromosomes differ from prokaryotic chromosomes
in important
ways
 Eukaryotic chromosomes are separated from the
cytoplasm by a membrane-bound nucleus
 Eukaryotic cells always have multiple chromosomes
 Eukaryotic chromosomes are longer and have more
DNA than prokaryotic chromosomes (human
chromosomes are 10 to 80 times longer and have 10
to 50 times more DNA)
 These differences account for the complexity of
eukaryotic cell division
How Is the DNA in Eukaryotic
Chromosomes Organized?
 The eukaryotic chromosome consists of a linear DNA
double helix bound to proteins





Each human chromosome contains a single DNA double helix, about 50 million to 250
million nucleotides long
Most of the time, the DNA in each chromosome is wound around proteins called histones
These DNA-histone spools are further folded into coils
Another layer of folding occurs as the coiled strand folds into loops, which are then
attached to protein scaffolding, so that the chromosome is 1,000 times shorter than the
extended DNA molecule
During cell division, more proteins fold up the DNA and histones, until it is 10 times
shorter than during its resting state
Figure 9-4 Chromosome structure
DNA double helix
histone proteins
DNA wound
around histone
proteins
Coiled DNA/histone beads
Loops attached
to a protein scaffold;
this stage of partial
condensation typically
occurs in a nondividing
cell
protein scaffold
Folded
chromosome,
fully condensed
in a dividing cell
WHAT DO THE FOLLOWING TERMS MEAN?
HOW ARE THEY RELATED?
.
DRAW THEM
 DNA GENES SISTER CHROMATIDS CENTROMERE
 CHROMOSOMES HISTONES LOCI TELOMERE-
GENES, CHROMOSOMES, and DNA
The DNA in a chromosome consists of two long strands
of nucleotides wound around each other, as a ladder
would look if it was twisted into a corkscrew shape
 This structure is called a double helix
 The units of inheritance, called genes, are segments
of DNA
 The specific sequence of nucleotides in genes spells
out the instructions for making the proteins of a cell
 When a cell divides, it replicates its DNA to make two
identical copies, and gives each daughter cell one of
the two copies
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 Genes are segments of the DNA of a chromosome
 Genes are sequences of DNA from hundreds to
thousands of nucleotides long
 Each gene occupies a specific place, or locus
(plural, loci) on the chromosome
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 In addition to genes, every chromosome has
specialized regions that are crucial to its structure and
function
 Two telomeres
 One centromere
 The two ends of a chromosome consist of repeated nucleotide sequences called
telomeres, which are essential for chromosome stability
9.3 How Is the DNA in Eukaryotic
Chromosomes Organized?
 Genes are segments of the DNA of a chromosome (continued)
 The second specialized region of the chromosome is
the centromere, which has two principal functions
1. It temporarily holds two daughter DNA double helices together after DNA
replication
2. It is the attachment site for microtubules that move the chromosomes during cell
division
Eukaryotes
 Chromosomes carry the DNA…but you need
two IDENTICAL COPIES of DNA to go to the 2
cells
 chromosome #
varies between
species
 humans46
chromosomes
(23 pairs)
REMEMBER: The life of a cell
 Before cells
can divide,
DNA needs to be replicated
So the code can be
passed on.
Which phase does this happen in????
 DNA Replication
 Process of copying a double stranded
DNA to form 2 double stranded
molecules
 Basis of biological inheritance used by
all living things
 Occurs before a cell divides (mitosis)

DNA Replication
1. Enzymes break the hydrogen bonds between the
bases so the chains of DNA can separate or
unwind

DNA Replication
2. Other enzymes add
new nucleotides,
which form new
hydrogen bonds
with their
complimentary
nucleotide.
Red = original strand
Blue = new strand

DNA Replication
 Results in 2 semi-conservative double
stranded molecules
WHAT IS THE ROLE OF:
HelicaseSSBReplication fork-
DNA Polymerase-
ANIMATIONS OF DNA REPLICATION
http://www.bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf
http://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swf
http://highered.mcgrawhill.com/sites/0072556781/student_view0/chapter11/animation_quiz_2.html
http://www.sinauer.com/cooper/4e/animations0601.html
AMEOBA SISTERS:
https://www.youtube.com/watch?v=5qSrmeiWsuc&index=1&list=PLwL0Myd7Dk1F1ppDaLx3ygO_7xA-yyd4