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FINDING DNA
National DNA DAY April 15, 2011
• National DNA Day
commemorates the successful
completion of the Human
Genome Project in 2003 and
the discovery of DNA's double
helix by James Watson and
Francis Crick in 1953.
Proof of DNA as Genetic Material
• Was the genetic material
protein or DNA?
• Mendel (peas) and Morgan
(flies) did not know it was
DNA.
Did you know…
• Every cell in your body has the
same DNA (you got it from Dad
and Mom).
• The reason the cells look different
is because different genes were
turned on.
Frederick Griffith
• A medical officer
was trying to find
a vaccine
against
pneumococcus
Rough and Smooth Pneumococcus
Griffith 1920’s
• Transformation
Griffith’s Conclusion
• harmless R cells (pneunomia) used the
genetic information from the dead S cells
and became harmful
• = transformation
= passing the
inheritance factor from one
organism to another
Oswald Avery
DNA
• He had reported that
, not
protein (which was believed at the
time), was the hereditary substance.
Oswald Avery 1940’s
Separated:
RNA
DNA
Protein
Caused S
strain to
cause
pneumonia
Simple centrifuge
video
Gave each to mice
Alfred Hershey and Margaret
Chase 1953
• Showed that the hereditary
material in bacteriophage viruses
is DNA.
• McGraw Hill Ani
Hershey-Chase
Animations
Hershey-Chase
• CONCLUSION –
• DNA is genetic material
32
because ( P) DNA
35
not ( S) protein guides
viral replication
Bacteriophages (“bacteria-eaters”)
Mostly
made of
just
protein
coat and
DNA
Virus Examples
• Cold Virus
HIV Virus
Bird Flu
Virus
Ebola Virus
Herpes Virus
Flu
Attack!
Bacteriophage Structure
Bacteriophage killing
bacteria
Virus: Are they Alive?
•Viruses can only
replicate in a living
host.
pp. 480-1 Bacteriophage Lytic
Infection
1.Attach to
host
2. Insert DNA
3. Make and
assemble
DNA parts
4. Lyse (burst)
Bacteriophage
Infection Video
Examples:
•Cold
•Flu
Lysogenic Infection
• BIOL 230 Lecture Guide - Lysogenic Life Cycle
of a Temperate Bacteriophage (animation link)
• 1. Virus lands on host.
• 2. Virus injects DNA into host.
• 3. Virus DNA attaches to host DNA =
prophage.
• 4. Virus Prophage will become lytic when
conditions are favorable (you are sick, tired).
Lysogenic Cycle Animation
• EXAMPLES:
HERPES
HIV
• GOOD ONE! McGraw Hill LyticLysogenic Animation
• Herpicide-SWEET
• Valtrex
Click on “Journey into DNA”
• NOVA Online |
Cracking the Code of
Life | Journey into
DNA (keep clicking on
“zoom” + button)
What is the structure of DNA?
• It is a nucleic acid
• Polynucleotide =
Made of long chains
of Nucleotides
DNA Nucleotide
Phosphate
Group
O
O=P-O
O
5
CH2
O
N
C1
C4
Sugar
(deoxyribose)
C3
C2
Nitrogenous base
(A, G, C, or T)
DNA Structure
• NUCLEOTIDE
• POLYNUCLEOTIDE
A Nucleotide
• MADE OF:
–Sugar
–Phosphate
–Base
• Deoxyribose sugar
• PO4
• 4 kinds:
• (A) (G) (T) (C)
(names on next slide)
4 Types of Base Pairs
• A = adenine
• T = thymine
• C = cytosine
• G = guanine
• NOW SING THE DNA SONG
Nitrogenous Bases
• PURINES -2 rings
1. Adenine (A)
2. Guanine (G)
A or G
• PYRIMIDINES -1 ring
3. Thymine (T)
4. Cytosine (C)
T or C
DNA
•Deoxyribonucleic
Acid
• (Get out colored pencils)
DNA Double Helix
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone
BONDS
Covalent
bonds join
Phosphates
and sugars
H-bonds
join N-bases
DNA Structure
• Rungs of the Ladder:
– Various orders of
A, T, C, G
• Backbone:
– Sugar and phosphates
– Alternate
DNA Double Helix
5
O
3
3
O
P
5
O
C
G
1
P
5
3
2
4
4
2
3
1
P
T
5
A
P
3
O
O
P
5
O
3
5
P
The other nucleic acid:
RNA
• Ribonucleic Acid
Three types:
– mRNA
(messenger)
– tRNA (transfer)
– rRNA
(ribosomal)
THE RNA’s JOBS
mRNA
rRNA
tRNA
Takes code
out of
nucleus to
ribosome
Part of the
Takes amino
structure of acids to
the ribosome ribosomes
Comparing DNA and RNA
• DNA
• RNA
• Double stranded
• Sugar =
deoxyribose
• Bases: A-T, C-G
• Found only in
nucleus
• Can repair itself
•
•
•
•
Single stranded
Sugar = ribose
Bases: A-U, C-G
Found in and out
of the nucleus
• Cannot repair itself
RNA
Making
mRNA
DNA
Pretty Similar
• Uracil • Thymine
DNA
- Contains Thymine
- Contains
deoxyribose sugar
- Double stranded
molecule
- Found only in
nucleus
Both
RNA
- Made of
nucleotides
- Single stranded
molecule
- Contain adenine,
guanine and
cytosine
- Contains uracil
- Contains ribose
sugar
- Found in nucleus
and cytoplasm
•
•
•
•
•
•
•
Relative Proportions (%)
of Bases in DNA Organisms
A
T G C
Human
30.9
Chicken
28.8
Grasshopper 29.3
Sea Urchin 32.8
Wheat
27.3
Yeast
31.3
E. coli
24.7
29.4 19.9
29.2 20.5
29.3 20.5
32.1 17.7
27.1 22.7
32.9 18.7
23.6 26.0
19.8
21.5
20.7
17.3
22.8
17.1
25.7
Question:
• If there is 30% Adenine, how much
Cytosine is present?
• HINT: A –T and C - G
Answer:
• There would be 20% Cytosine.
Adenine (30%) = Thymine (30%)
Guanine (20%) = Cytosine (20%)
Total of 100%
Chargaff’s Rules
• the amount of (A)denine will always equal
the amount of (T)hymine
• And
HOT!!!
• the amount of
(G)uanine will always
equal the amount
of (C)ytosine.
Nitrogenous Bases
• Why does A bond only with T and
C only with G?
• What do you notice?
Nitrogenous Bases
T and C are single-ring
Pyrimidines
A and G are double-ring
Purines
A single bonds with a
double
2 chains of nucleotides bind to form
a DNA molecule
• Hydrogen bonds form
between the
nitrogenous bases to
join the 2 chains
together
• The sugar and
phosphate group
together is known as
the sugar-phosphate
backbone
ENZYMES FOR DNA
REPLICATION
• Helicase = separates 2
DNA strands (breaks H
bonds)
• Primase=RNA primers at
INITIATION
REPLICATION ENZYMES
• Topoisomerase =
unwinding DNA
• DNA Polymerase = Adding
of DNA nucleotides
ELONGATION (proofread
and repair)
DNA REPLICATION ENZYMES
• LIGASE= Binds the
Okazaki fragments
• Watch the enzymes in
DNA Replication
Animation
AT and C-G Base Pairing
• DNA Replication simple version) (link)
• Media Showcase (cool animation link)
• Detailed Replication Link
DNA STRUCTURE
• A-T
• C-G
• in tons of
combinations
makes our
genetic code
DNA Replication
•Hi!...Still Awake?
•DNA Replication
Animation click here
What is the complementary base
sequence on the other strand of the
DNA?
A T T G C C C T A A
•
T
A A C G G G A T T
The Race is On!
• To Determine the Structure of the
DNA molecule.
DNA Geek
• Rosalind Franklin was an
English chemist who was
working in an X-ray
crystallography lab in Paris,
France in 1951.
FAMOUS
PHOTO 51
(correct
orientation
of DNAdouble
helix)
X ray Diffraction
Franklin’s Suggestion
DNA Geek
Maurice Wilkins (1916-2004)
• New Zealand Born British Scientist
• It was his idea to study
DNA by X-ray
crystallographic
techniques
• Nobel Prize
Linus Pauling
• American biochemist
suggested helix
(spiral)shape
• Most famous for
Vitamin C prevents
colds
DNA Geek
• Linus Pauling was a Caltech chemist
(USA), who in 1951 had discovered the
alpha helical nature of protein structure.
I remember his books: Vitamin C
and the Common Cold and Cancer
and Vitamin C also
The Nature of the Chemical Bond
and protested nuclear testing
DNA Geeks
• James Watson, a biologist from Indiana
University, and Francis Crick, a physicist,
were working at the Cavendish Lab in
Cambridge, England Nobel Prize for
structure of DNA
Francis Crick (1916-2004)
Narrative - 8. Watson and Crick - Linus Pauling and the Race for DNA: A
Documentary History
• Born in England
• Worked at Cambridge
Crick’s first
DNA
sketch
Worked on DNA structure
with Watson
James Watson (1928- )
• American age 22
• Ph.D. degree in Zoology in
1950
• Worked with Crick at the
King’s College on the
structure of DNA
• At age 12 starred on QUIZ
KIDS TV show
• Recently at Cold Spring
Harbor, NY, head of HGP
Watson and Crick
Met and worked at the
Cavendish Laboratory
Watson and Crick’s Wire Model
DOUBLE
HELIX
First put the
nitrogenous
bases on the
outside
(incorrectly)
DNA Bases
Franklin corrects Watson and
Crick
• Told them their first model was
incorrect
• They had put the bases on the
outside
The Scandal
• Watson used her pictures
(Photo 51) to determine that
DNA spirals into a double
helix.
•
Little did Rosalind
Franklin know that
her laboratory
colleague, Maurice
Wilkins, was in the
next room revealing
months of her work
to her competitor!
Rosalind Franklin
• Died of ovarian cancer at age
38 and so could not share in the
Nobel Prize
• Her work did lead the way to
work on viruses
• She was not included in the
publication that reported the
structure of DNA and she died
before the Nobel Prize was given
to Watson and Crick.
Nobel Prize
• In 1962 James Watson,
Francis Crick, and Maurice
Wilkins jointly received the
Nobel Prize in medicine or
physiology for their
determination in 1953 of the
structure of deoxyribonucleic
acid (DNA).
Violation of the
Scientists' Code of
Honor
•
It is necessary for scientists to share
information with one another, for if they did
not, science and knowledge would not
develop and grow. However, the tacit
agreement among scientists who use or
borrow one another's findings is that proper
credit must be given to the author or
originator of the work.
Beadle and Tatum’s Experiment
• used X rays to cause mutations in
strains of the mold Neurospora (a bread
mold)
• were able to create single gene
mutations that incapacitated specific
enzymes
Beadle and Tatum
The One Gene/One Enzyme Hypothesis
Beadle and Tatum
• Beadle and Tatum experiment animation
EXPLAIN:
•“The secret of life is
complementarity.”
Happy DNA
DAY
The day commemorates the
completion of the Human Genome
Project in April 2003, and the discovery
of DNA's double helix. DNA Song
NOVA | Ghost in Your Genes | PBS