Download Chapter 9

 Who was Gregor Mendel and what did he
discover?
 How many chromosomes are found in the
nucleus of each human body cell?
 During cell division, your cells DNA is replicated
during which part of the cell cycle?
 G1 (Growth Phase
 S (synthesis)
 G2
 After Mendel’s work, scientists wondered what
are genes made of?
 Through experimentation of scientists
**Griffith, Hershey, & Chase**, scientists
became convinced that genes were made of
DNA
 One question then arose….
 What is the structure of DNA?
I can – describe
the structure of
DNA

DNA
Structure
Knowing the structure of DNA
was important because it
clarified how DNA could
serve as genetic material
 Scientists **Watson &
Crick** pieced together a
model of the structure of DNA
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
DNA
Structure
Double helix- 2 strands
twisted around each other
(winding staircase)
 Each strand was made of
nucleotides. (subunits of
DNA)
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Each nucleotide is made of 3
parts.
◦ A phosphate group
◦ A five carbon sugar deoxyribose
◦ A nitrogen containing base
 Adenine (A)
Guanine (G)
 Thymine (T)
Cytosine (C)
◦ Draw & label the three parts of
a nucleotide in the box your
notes
The bases
are bonded
together by
weak
hydrogen
bonds
The sugar and
phosphate group
are the
“backbone” for
DNA
DNA
resembles a
ladder
twisted like a
spiral
staircase.
The bases
represent the
ladder’s
rungs
Adenine & Guanine
are considered
“Purines”
Cytosine &
Thymine are
“Pyrimidines”
The double helix is held together by
weak hydrogen bonds between the pair
of bases.
 Base pairing rules- Adenine pairs with
Thymine (A-T) Cytosine pairs with
Guanine (C-G)
 The sequence of bases on one strand
determines the sequence of bases on
the other strand.

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If the sequence on one strand of DNA can
determine sequence of other strand then….
One strand of DNA contains nitrogen bases
in this order..
A
What will the
T
complementary
G
DNA strand look
A
like?
C
C
If the sequence on one strand of DNA can
determine sequence of other strand
then….
 The second strand will look like this..
A
T
T
A
What type of bonds
G
C
hold these strands
of bases (the
A
T
ladder’s rungs)
C
G
together?
C
G

If the sequence on one strand of DNA can
determine sequence of other strand
then….
 The second strand will look like this..
T
G
What will the
C
complementary
strand look like?
G
A
T

If the sequence on one strand of DNA can
determine sequence of other strand
then….
 The second strand will look like this..
T
A
G
C
C
G
G
C
A
T
T
A

Create one strand of DNA with 8 nitrogen
bases. Have your partner complete the
complementary strand
T
A
G
C
C
G
G
C
A
T
T
A


Describe the 3 parts of a DNA
nucleotide

Name the bonds that hold together the
nitrogen bases in a DNA strand

List the abbreviations for the four
nitrogen bases of DNA

I can – explain the three steps in DNA
replication

I can – create two replicated strands of
DNA

Replication
of DNA
**Remember – DNA is
replicated during the “S”
(synthesis)phase in cell
division
 DNA Replication: making a
copy of DNA
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
Replication
of DNA

In DNA Replication, one
strand of DNA serves as the
“template” to build the
second strand of DNA

The replicated strand would
look like this

Replication
of DNA
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There are 3 steps in the
replication of DNA
In your group, assign a step to
each member
Use pages 198 – 199 to
describe your step in your own
words
Each member will also
describe how DNA “checks
for errors”
Share each step in order once
the whole group is finished
Result: 2 new
DNA double
helixes created
(identical to each
other and
original DNA)

What two enzymes play an important role
in DNA replication?

What is the purpose of DNA polymerase in
the “proofreading” role?
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What is the result of DNA replication?

What occurs in the first step of DNA
replication?
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Gene Scene
DNA Workshop
The Geee! In Genome
Putting DNA to work
Kids Genetics: DNA
Hershey and Chase Experiment Animation
DNA Replication Animation
Another DNA Replication Animation