DNA video project
SOME BACKGROUND INFO…
WHAT IS THE “STUFF” OF HEREDITY?
WHAT IS ITS STRUCTURE?
The following scientists helped to
answer these questions.
Griffith
Avery
Hershey-Chase
Watson, Crick
Wilkins and Franklin
Chargaff
I. GRIFFITH’S EXPERIMENT 1928
A. - make a vaccine against
harmful S. pneumoniae bacteria
1. virulent S strain (S. pneumoniae)
a. virulent means disease causing
b. capsule around the bacteria
provides protection from body
defenses
2. non virulent R strain (no capsule)
a. destroyed by body(can not cause
disease)
B. PROCEDURE and RESULTS
1. mouse injected with
R cells
2. mouse injected with
S cells
3. mouse injected with
heat killed S cells
4. mouse injected with
killed S cells mixed
with live R cells
mouse lives
mouse dies
mouse lives
mouse dies
Results of Griffith’s Experiment
C. C - Heat-killed S bacteria release
hereditary material that makes R strain
bacteria virulent
HOW???
1.Principle of Transformation
a. transfer of genetic material (DNA)
from one organism to another
b. DNA for making a capsule was
transferred from the S strain to the
R strain making it virulent
II. AVERY’S EXPERIMENTS (early 1940’s)
A – Is the transforming agent protein,
RNA or DNA?
B. PROCEDURE – (Three Experiments)
1. destroy 3 different molecules in the
heat-killed S strain bacteria and mix
with R strain bacteria
a. destroy protein (protease enzyme)
b. destroy RNA (RNase enzyme)
c. destroy DNA (DNase enzyme)
C. Results
1. Missing protein
a. transforms R cells to S cells
(mouse dies)
2. Missing RNA
a. transforms R cells to S cells)
(mouse dies)
3. Missing DNA
a. did not transform R cells to S cells
(mouse lives)
Oswald Avery
D. Conclusion – DNA is responsible for
the transforming principle
III. HERSHEY-CHASE EXPERIMENT
1952 (Martha Chase and Alfred Hershey)
– Is the hereditary material in viruses protein or
DNA?
B. PROCEDURE
1. Label protein and DNA in a phage with
radioactive isotopes (S-35 and P-32)
a. a phage is a virus that attacks
bacteria
b. S-35 labels protein and P-32
labels DNA
Martha Chase and Alfred Hershey used
Phage Viruses for Their Experiment
B. Procedure
2. Allow protein-labeled and DNAlabeled phage (virus) to infect E. coli
bacteria
3. remove and separate phage (virus)
from the bacteria (E. coli)
Hershey-Chase Experiment
- all viral DNA and a small amount of protein entered
the bacteria
D. CONCLUSION - DNA is the hereditary molecule in
viruses
IV. Watson and Crick (1953) /Wilkins and
Franklin
A. Watson and Crick
1. double helix model of DNA based on the
work of other scientists
B. Maurice Wilkins and Rosalind Franklin
1. x-ray diffraction photographs of DNA
helped Watson and Crick develop their
model
2. Watson, Crick and Wilkins received
Nobel Prize in l962 (Franklin died in 1958
and could not be named for the award)
X-ray Diffraction Photo
of DNA)
Rosalind Franklin
and Maurice Wilkens
DNA Double Helix
Watson and Crick
V. Erwin Chargaff - 1949
A. Percent of nitrogen bases that pair
with each other (complementary
bases) is the same
1. percent adenine equals percent
thymine
percent guanine equals percent
cytosine
2. implied base pairing rules
IV.
DNA
(Structure / Function)
Questions you should be able to answer…
1) Where is DNA located in the cell?
2) How is it arranged?
3) What is the purpose of DNA? What does it
do????
4) How many strands does it have and what
does it generally look like?
5) What is the basic building block of DNA
called and what three components make it
up?
6) What are the complimentary base pairs of
DNA?
Where is it located in the cell? NUCLEUS!
How is it arranged?
Chromosome - DNA
Chromosome-Chromatid
Purpose? To code for everything in your body...genetic blueprint!
 DNA Structure
1. Deoxyribonucleic acid is shaped like a
twisted ladder (double helix)

DNA Structure
2. DNA is a polymer made up of
monomers called nucleotides
Each nucleotide consists of:
a. a sugar called
deoxyribose
b. a phosphate
c. 1 of 4 nitrogen bases
(A, G, T, C)

DNA Structure
 Purine and pyrimidine
• adenine nitrogen bases
(purine)= thymine nitrogen
bases (pyrimidine)
• guanine nitrogen bases
(purine)= the cytosine nitrogen
bases (pyrimidine)

DNA Structure
 Erwin Chargaff: discovered
complementary base pair rules
• the # of adenine nitrogen bases
= the # of thymine nitrogen
bases
• the # of guanine nitrogen bases
= the # of cytosine nitrogen
bases
G= C
A=T
 DNA carries the
genetic code in its
sequence of bases
 What is the complementary
sequence of the bases listed
below?
AT T G C AA G C T C T G C

DNA Structure
3. The sides of the
DNA helix are
held up by
phosphates
and sugars
(deoxyribose)
Hydrogen bonds: hold
complimentary bases
together; very weak
and can be easily
broken
 DNA Replication
 Build a DNA molecule
 http://learn.genetics.utah.edu/conte
nt/begin/dna/builddna/
WE ALSO HAVE RNA in our
bodies
A. RNA contains
1. sugar molecule - ribose
2. phosphate
3. nitrogen bases
a. adenine and guanine
b. cytosine and uracil
B. The three types of RNA are:
a) messenger RNA (m-RNA)
b) transfer RNA (t-RNA)
c) ribosomal RNA (r-RNA)
Differences between DNA -RNA
DNA
RNA
Deoxyribose
Double strand
Thyamine
Ribose
Single strand
Uracil
DNA vs RNA
G= C
A=T
 But it’s the DNA
that carries the
genetic code in its
sequence of bases
GENES are
segments of DNA
that code for
characteristics!
GENES ARE SEGMENTS OF DNA
THAT CODE FOR A
CHARACTERISTIC, LIKE DIMPLES.
REALLY ITS THE ORDER OF THE
BASES IN THE DNA DETERMINE THE
CHARACTERISTIC. BUT
SOMETIMES PROBLEMS ARISE….
Mutations
A. Location of Mutations
1. somatic cell (body cell)
2. germ cell (cells that form sperm
and egg cells)
B. Causes
1. radiation
a. x-rays, alpha, beta, gamma
radiation, u.v. light
2. chemicals (mutagens)
3. DNA sequence changes in replication
C. Effects of Mutations
1. lethal (deadly)
2. may be beneficial
3. no effect
Point Mutation
change in one nucleotide …or change in a
base (A,T,C,G) in the DNA molecule
Types of mutations –
a. substitution – one base is
substituted for another
b. addition or insertion – an
extra
base is added
c. removal or deletion of a
base
Point Mutation:
Substitution of One Base