GETTING TO KNOW DNA:
A REVIEW
As you know, DNA stands for….
DEOXYRIBONUCLEIC
ACID
Is DNA a monomer or polymer
1. Monomer
2. Polymer
What does it mean to be a monomer?
What does it mean to be a polymer???
If we were reviewing proteins, the
monomer units would be:
1.
2.
3.
4.
Nucleic acids
Fatty acids
Sugars
Amino acids
If the monomer units of proteins
are amino acids, 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
I am sure you recall, we used 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!!!
THYMINE and CYTOSINE are smaller
molecules known as…
PYRIMIDINES
LOOK! Only one ring!!
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
In DNA GUANINE always pairs with
CYTOSINE using three hydrogen
bonds.
G
C
Time to use your brain and
hands in order to review
nucleotide structure and type.
OK
Now that you recognize
nucleotide type and structure, it’s
time to start building the polymer
from these monomers.
The molecules marked “W” are
best described as:
1.
2.
3.
4.
Monomers
Polymers
Isomers
isotopes
Reactions A and B
are respectively
known as:
A
1.
2.
3.
4.
Dehydration, hydrolysis
Condensation, hydrolysis
Polymerization, decomposition
Hydrolysis, dehydration
B
Molecule(s) “X” are most likely:
1.
2.
3.
4.
5.
Carbohydrates
Monomers
Polymers
Water
Starch
If molecule “W” is a nucleotide,
molecule marked “Y” is most likely:
1.
2.
3.
4.
5.
Protein
Starch
DNA
Galactose
Fructose
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
If you link enough nucleotides together,
the DNA molecule begins to take on
the characteristic shape known as the
Double Helix
Let’s Build
Some 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
A Particular strand of DNA contains 10
adenine molecules. How many thymine will
it contain:
1.
2.
3.
4.
5
10
20
Not enough information
A strand of DNA is 20% Guanine molecules.
What is the percent of thymine in the strand
of DNA?
1.
2.
3.
4.
5.
10
20
30
40
Not enough information
A particular strand of DNA is 40% guanine.
What is the percent of adenine in the same
strand?
1. 10
2. 20
3. 30
4. 40
The molecule at the location identified
by the arrow:
1.
2.
3.
4.
5.
Adenine
Guanine
Sugar
Phosphate
thymine
The molecule at the location identified
by the arrow:
1.
2.
3.
4.
5.
Adenine
Guanine
Sugar
Phosphate
thymine
The molecule at the location identified
by the arrow:
1.
2.
3.
4.
5.
Adenine
Guanine
Sugar
Phosphate
thymine
The end of the molecule identified by
the blue arrows:
1. Five prime
2. Three prime
The end of the molecule identified by
the red arrows:
1. Five prime
2. Three prime
Because the sides of the DNA ladder run in
opposite directions, DNA is said to be…
1.
2.
3.
4.
Parallel
Nonparallel
Antiparallel
proparallel
What is a
GENE?
Stay Tuned!! We will answer
this question tomorrow.