DNA: The Genetic Material
THE STRUCTURE OF DNA
Review:
ALL LIVING THINGS MUST
HAVE GENETIC MATERIAL.
Species must be able to
pass on that genetic
material to future
generations.
What do we remember about Nucleic Acids?
 Nucleic acids are polymers. What are the
monomers of nucleic acids?
 What are two examples of nucleic acids?
DNA Fun Facts!
 Most of our DNA is considered “junk DNA.”
 Humans share about 50% of the same DNA as
bananas.
 What does real (not microscopic) DNA look like?
Why is it important?
 It is why all living organisms look the way they
do!
 Prokaryotes- it codes for color, shape, whether
or not they have a flagella and so forth.
 It is why we behave the we do.
 The DNA sequences are the instructions of all of
our traits/characteristics.
What is DNA?
 WHO: Deoxyribonucleic Acid
 WHAT: Is a type of Nucleic Acid

WHERE: Is in ALL Living Organisms


Eukaryotes – located in the nucleus.
Prokaryotes- free floating in the cytoplasm
o
WHY: Used for storing and transmitting genetic
information

AKA: Genetic code
Genetic material
Blueprint for life
The molecule of inheritance



The Structure of DNA
Double helix
Building Blocks of DNA
 Nucleotides: subunits (monomers) that make
up the extraordinarily long thin molecule of
DNA

Each nucleotide is constructed of three parts:
1. A phosphate group
 2. A five-carbon sugar molecule (Deoxyribose)
 3. A nitrogen base (A,T,C, or G)

Building Blocks of DNA
 The five carbon
*The sugar-phosphate
backbone.
sugar molecule is
called deoxyribose.
 Phosphate group: is
attached to the sugar
and is the same for all
molecules of DNA
 These two molecules
form the backbone
of a DNA strand.
Building Blocks of DNA
 Nitrogen group- (the rungs of a ladder)
has four possible configurations:
Adenine (A)
 Guanine (G)
 Thymine (T)
 Cytosine (C)

Building Blocks of DNA
 Purines: a class of
organic molecules
that have a double
ring of carbon and
nitrogen atoms


Adenine
Guanine
Building Blocks of DNA
 Pyrimidines: a class
of organic molecules
that have a single
ring of carbon and
nitrogen


Thymine
Cytosine
Base Pairing Rule
13
 Adenine must pair with Thymine
 Guanine must pair with Cytosine
* These bases are linked by weak
hydrogen bonds.
T
copyright cmassengale
A
G
C
Chargaff’s Rule

The amount of Guanine
always equals the
amount of Cytosine
(number of G = number
of C).

The amount of Adenine
always equals the
amount of Thymine
(number of A = number
of T).
Why are the bases so picky?
DNA is a Double Helix
 Double Helix:

Has a sugar and phosphate
backbone
 Adenine pairs with Thymine
 Guanine pairs with Cytosine
 The Nitrogen bases (A-T and
C-G) are held together by
weak hydrogen bonds.
 Due to the base pairing the
two strand are
complementary to each
other.
Rosalind Franklin 1951-1953
 Scientist who used X-Ray diffraction
to help contribute to the discovery
that DNA is a double helix.
DNA is a Double Helix
(question 2)
 1953: Watson and Crick
 Using the base pairing rule
and X-ray photos from
1950 made a 3-D model
using tin and wire

The result was the double
helix, a “spiral staircase”
configuration
Let’s Practice!
 Write the complementary strand for the
following sequence:
 AGTCCTGAAATCGG
 TCAGGACTTTAGCC