Cell cycle, DNA, and
replication
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?
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?
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
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
COMING UP IN THIS CLASS…
 In the upcoming months, we will be analyzing what happens stages
in great detail. Which stage do you think the following upcoming
material will focus on?
Topics to cover:
- Cell cycle and events
- DNA structure and replication?
- DNA structure
- Cell reproduction (asexual- bacteria)?
- Cell reproduction (growth- multicellular)?
- DNA and making proteins
- Proteins and regulation of the cell cycle
- What happens when things go wrong….
NUCLEIC ACIDS: The 4th category
of Biomolecules
 What were the 4 macromolecules/biomolecules?
 What are monomers? Polymers?
 What is the name of the process that builds monomers to
polymers called?
 What is the reverse process called?
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 Nucleic Acids are the chemical link between generations dating
back to the beginning of life on earth.
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A nucleic acid is a
complex
macromolecule that
stores information in
cells in the form of a
code.
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Terminology:
 What is the difference and relationship between the following:
-
DNA
Chromosomes
Genes
Centromere
nucleotides
-nucleus
- chromatid
- chromatin
-histones
What are chromosomes???
Nucleotides make up DNA
DNA winds into Chromatin
Chromatin condenses into Chromosomes are
composed of chromatids held together at the
centromere
Chromosomes contain Genes
Genes are sections of DNA
DNA is made of nucleotides
Chromosomes contain
Instructions for making
YOU!!!
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Where is it located in the cell? NUCLEUS!
How is it arranged?
Chromosome - DNA
Chromosome- Chromatid
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
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NUCLEIC ACID
 What is the monomer of nucleic acids called?
 What components does it have?
 What are the 2 major nucleic acids?
 What do they do?
 What ways are they similar in structure?
 What 3 ways do they differ in structure?
THEME….how is the structure related to their function?
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 MONOMER: Nucleic acids are made of long chains of
nucleotides.
 Nucleotides are made of three components:
1. sugar
2. phosphate group
3. nitrogen base
 Examples of nucleic acids are :
1. DNA
2. RNA
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Purpose? To code for everything in your body...genetic blueprint!
DNA = deoxyribonucleic acid
its components are:
1. deoxyribose (sugar)
2. phosphate group
3. nitrogen base
The Components and Structure of DNA
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There are four kinds of
bases in in DNA:




adenine
guanine
cytosine
thymine
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Adenine (A) – Thymine (T)
Guanine (G) – Cytosine (C)
A and G are purines (AGgies eat Purina)
C and T are pyrimidines
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The paired nitrogen
bases formed two
long strands of
nucleotides that
compliment each
other.
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Nitrogen Bases are connected
between sugars and phosphates
They declared, “This structure is
a “double helix”
The structure is antiparallel (upsidedown).
This causes a problem in replication
Because replication is a one way
direction.
DNA Double Helix
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WHO DISCOVERED THIS???
 …..its complicated
IV. Watson and Crick (1953) /Wilkins and Franklin
A. Watson and Crick
1. double helix model of DNA based on the
work of other scientists
B. Maurice Wilkins and Rosalind Franklin
1. x-ray diffraction photographs of DNA
helped Watson and Crick develop their
model
2. Watson, Crick and Wilkins received
Nobel Prize in l962 (Franklin died in 1958
and could not be named for the award)
X-ray Diffraction Photo
of DNA)
Rosalind Franklin
and Maurice Wilkens
DNA Double Helix
Watson and Crick
CHARGAFF:
Percent
of nitrogen
bases that pair
with each other
V. Erwin
Chargaff
- 1949
(complementary bases) is the same
1. percent adenine equals percent thymine
percent guanine equals percent cytosine
2. implied base pairing rules
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 DNA forms chromosomes, units of genetic information which
pass from parent to offspring.
DNA is wound into
structures called
chromosomes during
cell division
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 If you unraveled all your chromosomes from all of your cells
and laid out the DNA end to end, the strands would stretch
from the Earth to the Moon about 6,000 times.
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 RNA has a different sugar than DNA
 RNA = ribonucleic acid
 It’s components are :
1. ribose (sugar)
2. phosphate group
3. nitrogen base
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 It also has different bases than DNA
adenine --- uracil
cytosine --- guanine
 RNA is also single stranded, not double stranded like DNA.
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DNA
RNA
- Double stranded
- Single stranded
- Sugar =
deoxyribose
- Adenine pairs with
Thymine
- Sugar = ribose
- Adenine pairs with
Uracil
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I. Why Must DNA Replicate?
 Every time a cell divides, it must first make a
copy of it’s chromosomes.
 Therefore, each cell
can have a complete set
of chromosomes.
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 Without replication, species could not survive and individuals
could not successfully grow and reproduce.
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II. How DNA Replicates
DNA is a molecule composed of TWO strands,
each consisting of a sequence of nucleotides.
The order of the nitrogen bases on one
strand mandates the sequence of bases on
the complementary strand.
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If you know the bases on one strand, you can predict which bases will occur on the
complementary strand.
A
G
T
C
C
C
T
-----------------------------
T
C
A
G
G
G
A
During Replication each strand serves as a template to create a new strand.
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III. Steps In
Replication
1) Helicase break
down the hydrogen
bonds between the
two DNA strands,
unzipping the
molecule

DNA Replication
1. Helicase break the hydrogen bonds between the
bases so the chains of DNA can separate or
unwind
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2) As the DNA unzips,
SSB (single strand
binding protein holds
the strands down.
3) Primase(RNA)
makes start
platforms
4) DNA polymerase adds nucleotides (from surroundings in the
nucleus) bond to the single strands by base pairing (A-T, GC)
SEMI- CONSERVATIVE REPLICATION:
** The result of this process is the formation of TWO DNA
molecules, each identical to the original molecule- with one
old strand and one new strand.
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
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.s
wf
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=PLwL0Myd7Dk1F1p
p-DaLx3ygO_7xA-yyd4
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1. What are the two types of nucleic acids?
2. What are the three components of a
nucleotide?
3. What are the similarities between DNA
and RNA? What are the differences?
4. Describe the process of DNA replication.
5. Why does a DNA molecule undergo
replication?