Do Now!!  (period 2 & 6)
 What
does DNA stand for?
 What
is the shape of DNA in eukaryotic cells?
In prokaryotic?
 How
is DNA considered a “blueprint”?
Objectives
 To
define DNA and understand its significance
 To summarize the experiments of Griffith and
Avery leading to discovery of DNA as genetic
material
 To introduce viruses and their characteristics
Ch. 12:
Molecular
Genetics!!
Activity!
 With your group members, please answer the
questions about DNA in the table.
 We will come together as a class to complete the
table!
DNA
 DNA:
Deoxyribonucleic acid
 Located in the nucleus of cells:
 If
red blood cells don’t have a
nucleus, how can we test blood for
DNA?
 The
function of DNA is to tell the
cells how to produce things that
make you up (Blueprint):
 How to make proteins!
When was DNA discovered, and who
discovered such a glorious thing?
 Scientists tried to determine the source of genetic
information:

Nucleic acid (DNA) or proteins??
Do Now!!  (period 6)
 Is bacteria living or non-living?
 What shape does bacterial DNA have?
 What do we mean by “strains” of bacteria?
Objectives
 To
define DNA and understand its significance
 To summarize the experiments of Griffith and
Avery leading to discovery of DNA as genetic
material
 To extract DNA from strawberries
1928 Frederick Griffith:
 First
major experiment that led to discovery of DNA
 Studied two strains of the bacteria Streptococcus
pneumoniae (causes pneumonia):



Rough strain (R) and Smooth strain (S)
S strain has protective outer coating, R strain does not
S strain causes pneumonia and the R strain does not
What do you
think
happened??
1928 Frederick Griffith:
 Discovered
that the heat killed S type
bacteria was turning the R type bacteria
into smooth!!
 Called it the transforming factor
 Set up stage for search to find this
transforming substance
1944 Oswald Avery:
 Purified
protein, RNA, and DNA separately from
Streptococcus pneumonia bacteria to determine
which would transform the harmless bacteria.
 destroys proteins  mice died
 RNase  destroys RNA  mice died
 DNase destroys DNA  mice survived
 Protease
 Conclusion:
DNA is the genetic material!!
Nobody believed Avery
 His
conclusions were not widely accepted in
scientific community.
 Other scientists tried to determine what this
transforming factor was!
 Is it protein or DNA?
 Lets ask Hershey and Chase!
Do Now!! 
 Which strain of bacteria killed the mice in
Griffith’s experiment?
 What happened
to the R strain that caused
death in the mice? What is that called?
 What conclusion did Avery reach?
Objectives
 To identify the 6 characteristics of viruses
 To define and label a bacteriophage
 To determine the 5 stages of viral attack!
Hershey and Chase
 Worked
with viruses to determine what the
“transforming factor” was.
 What
is a virus, and how does it work??
T4 bacteriophage
Martha Chase and Alfred Hershey
6 Characteristics of Viruses
 1.
Have their own genome (genetic make up)
made of either DNA or RNA
 2. Do not have enzymes, ribosomes, or ATP
 3. Have external protein shells (capsids)
T4 bacteriophage
HIV
Rhinovirus
6 Characteristics of Viruses
 4.
Infect only specific cells
 5. 2 life cycles (lytic and lysogenic)


 6.
Lytic – breaks out and spreads (destroys the cell)
Lysogenic- hangs around (does not destroy cell)
Smaller than bacteria
Ebola Virus
Influenza
Measles
Do Now!!  (period 2)
 What are the 6 characteristics of a virus?
 What is the difference between lysogenic and
lytic life cycles of a virus?
Objectives
 To define and label a bacteriophage
 To identify the 5 stages of viral attack
How a virus attacks!
 https://www.youtube.com/watch?v=Rpj0emEGS
hQ
Bacteriophage: a virus that attacks bacteria
Capsid head
DNA
Protein coat
Tail sheath
Tail fibers
Lytic and Lysogenic cycles:
Do Now!!  (period 2 & 6)
Please label the structure below
Objectives
 To identify the 5 stages of viral attack
 To discuss the importance of Hershey and
Chase’s experiment
5 Stages of Attack!
1) Attachment: virus attaches to its host
2) Injection: virus injects its DNA into the host cell.
3) Replication: virus copies its genetic material many
times.
4) Assembly: virus assembles more viruses
5) Release: Viruses are released from the cell, ready to
attach to new cells!
Bacteriophage attack
 https://www.youtube.com/watch?v=Ms2xhuKq
mDI
Worksheet!
Do Now!! 
 What are the 5 stages of attack for a virus?
 Label the pictures below with the 5 stages!
Objectives
 To
discuss the importance of Hershey and
Chase’s experiment
 To identify the importance of radioactive
labeling
1952 Hershey and Chase
 Radioactive
Labeling:
 Replacing atoms with radioactive isotopes
 Radioactivity acts as a label
 Make note!
 Proteins contain sulfur (in certain amino acids)
 DNA contains phosphorus (in backbone)
Sulfur
Methionine
Cysteine
Phosphate
Hershey and Chase
 Radioactive
Labeling:
 Used radioactive phosphorus (32P) to identify
DNA in the bacteriophages
 Used radioactive sulfur (35S) to identify proteins in
the bacteriophages
 Radioactive
bacteriophages infected bacteria cells
 Used radioactivity to identify movement of proteins
and DNA
1952 Hershey and Chase
 They
found radioactive sulfur
outside of bacteria cells and
radioactive phosphorus inside
bacteria cells
 Only radioactively labeled DNA was
inside of the bacteria cell
 Therefore, DNA is genetic
material!!
Do Now!! 
 Take out your scientists packets and fill
out the section on Hershey and Chase!
Objectives
 To identify the structure of DNA
 To label a molecule of DNA
 To define chromosomes and their structure
Now we know DNA carries genetic material!
Soooo now what?
 Phoebus
Levene discovered that DNA is
made of nucleotides
 DNA is a nucleic acid…
 So what are nucleotides?
DNA Structure
 Nucleotides:



5 carbon sugar (Deoxyribose)
Phosphate Group
Nitrogen base
Nitrogenous Bases
 Purines
 Have 2 rings (double ring structure):
Adenine (A)
b. Guanine (G)
 Pyrimidines
 Have 1 ring (single ring structure):
a. Thymine (T)
b. Cytosine (C)
c.
Uracil (U) instead of Thymine in
RNA
a.
DNA Structure
Chargaff’s Rule
 Erwin Chargaff
 Discovered that A pairs with T
and C pairs with G.
 Chargaff’s rule:
 A=T, C=G
 Amounts vary between
species
Draw in the complimentary sequence
AT G C TAAT T C AT G AA C
Do Now!! 
 What makes up a nucleotide?
 What is the difference between purines and
pyrimidines? List them!
 Compliment the following sequence:
A T G C A A A T G C G A C C
Objectives
 To discuss Rosalind Franklin’s contribution to
discovering the structure of DNA
 To identify the accomplishments of Watson and
Crick
 To define a chromosome and label its important
parts
Rosalind Franklin
 Used X-ray diffraction
to
determine shape of DNA
 X-ray diffraction:
 X-rays aimed at molecules,
bounce off electrons
 Determines the molecule’s
shape
Rosalind Franklin
 Took now famous photo 51
 Data indicated that DNA was
a double helix shape
 Helped Watson and Crick
solve the structure of DNA
Watson and Crick
 Built a model of the double helix
DNA molecule:
 two outside strands consist of
alternating sugar and
phosphate molecules
 thymine and adenine bases
pair to each other by two
hydrogen bonds
 cytosine and guanine bases
pair to each other by three
hydrogen bonds
DNA Structure
 DNA looks like a twisted
ladder
 Rails: alternating
deoxyribose sugars and
phosphates
 Rungs (steps): base pairs
(C-G, A-T) bonded by
hydrogen bonds
Label the parts of the DNA molecule
Orientation of DNA- Anti Parallel
o On the top rail, the strand is said to be
oriented 5′ to 3′.
o The strand on the bottom runs in the
opposite direction and is oriented 3′ to 5′.
o 5′: exposed phosphate group
o 3′: exposed hydroxyl group (-OH)
Chromosome Structure
 DNA coils
around histones (proteins) to form
nucleosomes
 This coils to form chromatin fibers
 The chromatin fibers supercoil to form chromosomes
that are visible in the metaphase stage of mitosis.