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Polymers
DNA Structure and Function
History of DNA
 Scientists were aware that DNA had a sugar
phosphate background and had bases A, T, G and
C but were not sure about the actual shape of DNA.
 Wilkins and Franklin used X-ray crystallography to
create images of DNA’s structure.
 Watson discovered that the base pairs A to T were
exactly as long as G to C. Causing each rung to be
of equal length
Founders

Now that they had the shape – helical or
twisted ladder – and the base pairing rule,
they could share with the scientific
community the shape of DNA.
NOBEL PRIZE awarded to Watson and Crick
shared with Wilkins and Franklin for
discovering the shape of DNA.
Nucleic acids


DNA –
Deoxyribonucleic
Acid – a simple
polymer
the “molecule of
heredity.”
DNA Animation
http://www.youtube.com/w
atch?v=lhrLs03KjY&feature=r
elated
Job of DNA
 Stores information
on how to make
proteins; the
building–blocks of
living organisms
Hydrogen Bonds
phosphate
Sugar
SHAPE – Double helix
What is a Monomer
 the simple building
blocks used to hook
together to build long,
complex polymers
ex. Keratin (protein in hair),
Nylon, plastics,…
What is a Nucleotide?
The monomers that builds up the DNA polymers
What are the components found in nucleotides?
 Sugar
 Phosphates
 Bases
O
A Nucleotide
H
CH3
N
O
O
O
N
CH2
O
C
OH
C
C
C
OH
O
P
OH
OH
Sugar
Phosphate
C6H12O6
HOCH2
OH
O
C
H
C
C
Found on DNA
HOCH2
C
C
H
OH
OH
OH
O
C
C
C
OH
Sides of the ladder
Backbone of DNA
Ribose
Deoxyribose
DNA is found in the Nucleus
Types of Bases
Uracil – only
Adenine
in RNA
NH2
OH
N
N
N
N
N
HO
H
Guanine
Thymine
OH
N
N
Cytosine
O
N
H2N
N
H
NH2
CH3
N
N
N
O
H
N
H
HO
N
Purines and Pyrimidines
Purines- double ringed
Pyrimidines – single ringed
Which Bases Pair
Together
A=T
C=G
Why do they pair together?
Hydrogen bonds
A = T has two bonds
G = C has three bonds
Anti-parallel-What does it
mean?
What are Genes?
Long stretches of DNA that are “recipes” for
how to build a specific protein.

For example: the gene for Kertain is a stretch
of DNA with instructions for building a Keratin
molecule
Summary Flow Chart
How are genes, proteins,
traits, DNA and
chromosomes related?
 traits are the result of proteins
 Proteins are determined by a stretch of
DNA called a gene.
 Genes are stretches of DNA on a
chromosome.
 DNA codes for the proteins that make up
traits
What could happen if genes
had the wrong sequence of
nucleotides?
 Incorrect proteins could be made. This
could lead to disease, spontaneous
abortion, cancer or death.
Called a Mutation
 When does DNA remake itself?
 Interphase
 3 parts to Interphase
 G1 – cell carries out
normal functions
Mitosis
G2
Cell Cycle
 S – DNA is copied
 G2 – Cell carries out
normal functions
S
DNA Synthesis
G1
 What must be present for DNA to remake itself?
 Original
Original DNA
 Ink and paper
Nucleotide
 Photocopier
DNA
Polymerase
 Original Strand
The original strand is used as a
template
Example:
 A nucleotide is the sugar, phosphate and base.
 Where do the “free” nucleotides come from?
 From the food that we eat
 Adenine, Thymine, Cytosine, Guanine
 What is an enzyme?
 An enzyme is a protein
 “Cellular Machine” that can build up or
tear apart molecules.
DNA replication wrap up
http://www.youtube.com/watch?v=hfZ8o9D1tus
a. Template (original) Strand – original strand used
to tell what nucleotide to add
b. Newly Synthesized (copy) Strand – just being
built, a copy of the original strand
 What happens
during DNA
replication?
a. - DNA unzips
 Helicase
unwinds DNA
double helix;
breaks
hydrogen
bonds
b. - DNA polymerase attaches to DNA
c. DNA polymerase copies DNA
• Free nucleotides find their compliments on each
side of the DNA strand
New bases keep attaching
until two identical
molecules of DNA are
created.
This is called semiconservative replication.
THE RESULT:
2 new DNA molecules, each is ½ old
strand, ½ new strand
Mitosis then follows where each cell
gets copy
1
2
A–T
T–A
G–C
A–T
C-G
A
T
A– T
A -T
T
A
T– A
T -A
G
C
G– C
G -C
A
T
A– T
A -T
C
G
C– G
C -G
DNA unzips
•Hydrogen bonds
broken
DNA is copied
•Free nucleotides
attached
A–T
T–A
G–C
A–T
C-G
A
T
A– T
A -T
T
A
T– A
T -A
G
C
G– C
G -C
A
T
A– T
A -T
C
G
C– G
C -G
Template Strand
Template Strand
•Old DNA strand
A–T
T–A
G–C
A–T
C-G
A
T
A– T
A -T
T
A
T– A
T -A
G
C
G– C
G -C
A
T
A– T
A -T
C
G
C– G
C -G
Copy Strands
• New DNA Strand
 Reads in an antiparallel direction
when bringing in free
nucleotides
EX:
 http://www.dnalc.org/view/15509-DNAreplication-animation-3D-animation-withbasic-narration.html
Video
http://www.youtube.com/watch?v=zdDkiRw
1PdU&feature=related
Song:
http://www.youtube.com/watch?v=dIZpb9
3NYlw&feature=related
ANIMATIONS
http://www.contexo.info/DNA_Basics/DNA%20Replication.htm
http://www.teachersdomain.org/sci/life/gen/mechdna/index.html
Proteins

Subunits of life
Monomers – Amino Acids
Polymers – many A.A. joined together to form
a polypeptide chain
To Recognize
 Amino group NH2 or NH (circle in green)
 Carboxyl COOH or CO (circle in red)
These are the
“side chains”
or R groups –
makes each
amino acid
different from
one another
Proteins – long chain of amino
acids bonded together

Peptide bond (Circle in figure
below)
Amino
Acid
Amino
Acid
Amino
Acid
Amino
Acid
Amino
Acid
Amino
Acid
Amino
Acid
Peptide Bond
Organisms build proteins
from 20 amino acids
 Flip and look at the
page with our 20
amino acids.
 Don’t need to
memorize these, but
notice……ALL have
an NH2 and a COOH
group.
Why are protein important?
 Enzymes – speed up biological reactions
 Antibodies – immune system
 Channels – allow ions through cell
membrane by creating channels
Types of Proteins
Enzymatic (speed up/control chemical reactions)

Catalase – located in plants, animals and
aerobic bacteria to break down hydrogen
peroxide (otherwise harmful, toxic) into water
H2O2  H2O + O2
and oxygen
H2O2 poison builds up as
we digest food
•In the liver H2O2 is changed
to water and oxygen by
Catalase
 Rhodopsin – a protein in the membrane in the
photoreceptor cell in the retina in the eye. This
part changes shape when light hits it and
leads to a nerve impulse to being transmitted
to the brain

Structural (our building blocks) actin and
myosin work together to help the muscle
cells relax and contract

Oxygen Carriers – Hemoglobin is two
proteins (alpha and beta) are in red blood
cells that “stick together” They carry oxygen

Hormones (send signals) – Insulin- binds and
changes shape of receptor to form a tunnel to
allow entry of molecules such as glucose into
the cells.
Now that you understand:
 What determines the role or function of a
protein?
Shape
 What determines the shape of a protein?
Function