GETTING TO KNOW DNA:
Below is one of the molecules that makes up DNA.
What functional groups do you see in the
molecule:
11%
11%
79%
0%
1.
2.
3.
4.
Hydroxyl
Carboxyl
Amino
Phosphate
Which of the following contains the
most variety of essential elements
0%
0%
100%
0%
1.
2.
3.
4.
A
B
C
D
A
B
D
C
As you know, DNA stands for….
DEOXYRIBONUCLEIC
ACID
Functions of DNA
• Control the processes of heredity by which
cells and organisms reproduce proteins
Types of Nucleic Acids
1. DNA
(deoxyribonucleic
acid): doublestranded
2. RNA (ribonucleic
acid): singlestranded
Nucleic Acid Structure
• The monomer units of DNA are known as
nucleotides
• All nucleotides have three “parts” in
common:
a. Phosphate
b. Pentose sugar
a. (ribose or deoxyribose)
c. Nitrogen base
Deoxyribose Sugar (DNA)
• Has 5 carbons
• Carbon atoms are numbered 1', 2', 3', 4',
and 5'
• 5'-carbons link to the phosphate groups
• 3'-carbons link to the hydroxyl groups
Is DNA a monomer or polymer
21%
79%
1. Monomer
2. Polymer
What does it mean to be a monomer?
What does it mean to be a polymer???
What type of reaction is being shown below?
O
53%
42%
5%
iz
a
ly
m
er
nt
he
s
Po
Sy
n
yd
ra
tio
eh
is
is
ro
ly
s
yd
H
D
t
xi
da
O
tio
n
0%
tio
n
0%
al
en
Covalent
Oxidation
Hydrolysis
Dehydration Synthesis
Polymerization
ov
1.
2.
3.
4.
5.
0
C
O
The molecules marked “Y” and “W”:
58%
5%
0%
5%
32%
1.
2.
3.
4.
5.
Polymers and monomers
Water and polymer
Water and monomer
Water and water
Monomers and polymers
The monomer units of DNA are
known as….
NUCLEOTIDES
All nucleotides have three “parts” in
common. They all contain….
One of FOUR different
NITROGEN BASES
Phosphate Group
Sugar= Deoxyribose
PLEASE UNDERSTAND, A NUCLEOTIDE IS
A VERY COMPLEX STRUCTURE. IF WE
REPRESENTED ALL OF THE ATOMS, IT
WOULD LOOK LIKE THIS…
Let’s Practice How to Form
DNA!
We will use our hands to represent a
nucleotide.
PHOSPHATE
NITROGEN
BASE
SUGAR
The four different Nitrogen Bases for DNA
are abbreviated using the following letters….
A
Adenine
T
Thymine
G
Guanine
C
Cytosine
Using your two hands, please show how
you think two nucleotides will/should bond
together.
Did you put your hands like this???
Time to find out why this is
wrong!!!
Adenine and Guanine are larger
molecules known as…
PURINES
LOOK! TWO RINGS!!!
b. Purines: combination of a pentagon
shaped ring and a hexagon shaped ring
1. Adenine
2. Guanine
THYMINE and CYTOSINE are smaller
molecules known as…
PYRIMIDINES
LOOK! Only one ring!!
Nitrogen Base Pairing
• Adenine and Thymine must form two
hydrogen bonds to be stable while
Guanine and Cytosine must form three
– Makes the base pairing system an extremely
simple: the A-T and C-G pairs are the only
ones physically possible
Now, when using our hands to represent the
nucleotides, we must modify the nitrogen
base in order to represent these PURINES
and PYRIMIDINES.
How would you
represent a large
PURINE?
How would you
represent a small
PYRIMIDINE?
Full Finger
Half Finger
In DNA, a PURINE always bonds with a
PYRIMIDINE when forming a “rung” of the DNA
ladder.
LOOK! A long finger pairs with a short finger! In
other words, a purine pairs with a pyrimidine.
In DNA, Adenine always pairs
with Thymine using two hydrogen
bonds.
A
T
A AND T AT THE ATOMIC LEVEL
In DNA GUANINE always pairs with
CYTOSINE using three hydrogen
bonds.
G
C
G AND C AT THE ATOMIC LEVEL
THE
ENTIRE
MOLECULE
AT THE
ATOMIC
LEVEL
Time to use your brain and
hands in order to review
nucleotide structure and type.
USING YOUR HAND, SHOW ME THYMINE
USING YOUR HAND SHOW ME ADENINE
SHOW ME CYTOSINE
SHOW ME HOW CYTOSINE AND THYMINE BOND
TO FORM A RUNG ON THE LADDER
THEY DON’T
OK
Now that you recognize
nucleotide type and structure, it’s
time to start building the polymer
from these monomers.
In order to make a molecule of DNA,
you would need to create many rungs
to the DNA ladder.
Look. Many Rungs.
Etc…
What part of the nucleotide alternates
to form the sides of the DNA ladder?
Sugar, Phosphate.
Sugar, Phosphate.
Sugar, Phosphate.
Etc…
Etc…
What makes up the
“RUNGS” of the ladder?
The Nitrogen
Bases
Go Ahead!
Stack you hand on top of your partners
hands building two rungs of the DNA
ladder.
Why is this
WRONG????
The sides of the DNA ladder “run” in opposite
directions. One side is actually flipped and the
nucleotides are upside down!
TRY IT!!!
Because the sides of the DNA “run” in
opposite directions, DNA is said to be
ANTIPARALLEL.
In this DNA molecule, the THUMB part or
better known as the PHOSPHATE
GROUP, is said to be the 5 prime (5’) end.
5 prime
5 prime
The “hand” or sugar part of the DNA
molecule makes up the 3 prime (3’) end of
the DNA ladder.
3 Prime
3 Prime
• Direction of the nucleotides in one strand
is opposite to their direction in the other
strand: the strands are antiparallel.
• Asymmetric ends of DNA strands are
called the 5′ (five prime) and 3′ (three
prime) ends
– 5' end having a
terminal phosphate group
– 3' end having a terminal
hydroxyl group
If you link enough nucleotides together,
the DNA molecule begins to take on
the characteristic shape known as the
Double Helix
Let’s make a candy version of
our DNA
You Need…
•Two Pipe cleaners
•Two red twizzlers
•Two black twizzlers
•Many toothpicks
•Four different colored marshmallows
The marshmallows represent the
nitrogen bases. Let’s decide as a
class what colors will represent the
following nitrogen bases.
ADENINE=
CYTOSINE=
THYMINE=
GUANINE=
Person One
Cut the black twizzlers into 1.5 cm pieces.
These will represent the phosphate groups
Person Two
Cut the red twizzlers into 3 cm pieces.
These will represent the sugars.
Add the twizzlers to the pipe cleaners.
Remember, you need to alternate
SUGAR (red) AND PHOSPHATE
GROUPS (black).
When you are finished, your strand
should not end in the same color you
started with!
Did you and your partner make
the same number of nucleotides
on the sides of your ladder?
If not, FIX IT!!!
Time to put together the two sides.
Using the toothpicks and marshmallows, you are to
add the nitrogen bases to the sides of the ladder.
Remember, the nitrogen bases “come off” the sugar
part of the nucleotide. As a result, they should be
coming off of the red twizzler.
Please use two of the same color
marshmallows to represent one ADENINE and
GUANINE. The BIG purines.
Please use only one marshmallow to represent
THYMINE and CYTOSINE. The small
pyrimidines.
Following your teachers
directions, let’s build one
long strand of DNA
What is a
GENE?