Download Document

The History and
Structure of DNA
EQ: How is DNA constructed?
What does the DNA of all these
organisms have in common?
They all share a universal
genetic code.
History of Heredity
Why am I so
gorgeous?
Gregor Mendel
Gregor Mendel
determined that
traits were
passed from
generation to
generation.
But, I haven’t
figured out
how this
happens
Frederick Griffith
Griffith was working on a vaccine
for Streptococcus pneumoniae
He worked with 2 strains of the
bacteria:
A disease causing a strain
which grew in smooth colonies
A harmless strain that grew in
rough colonies
Frederick Griffith
He added these bacteria strains,
some dead and some living, to lab
rats.
These are his results:
Frederick Griffith
Live
Smooth
Bacteria
Live
Rough
Bacteria
Dead
Smooth
Bacteria
Live R+
dead S
Bacteria
Griffith Proved:
That somehow the dead bacteria
have passed their disease-causing
substance to the harmless, living
bacteria. We now know this as
“transformation”.
Griffith discovered that transformation
could transform harmless bacteria into
disease-causing bacteria
This substance was later determined to be DNA!
DNA
Erwin Chargaff
DNA nucleotides are made up of 4 different
nitrogen bases (adenine, thymine, cytosine,
guanine)
Chargoff discovered that DNA has the same
amount of adenosine as thymine and the
same amount of cytosine as guanine. A = T
and G = C
AA
A
A AA
A
TT
T
T T TT
C
CC
GG
G
Rosalind Franklin &
Maurice Wilkins
Rosalind Franklin
Franklin and
Wilkins used
x-ray to
discover that
DNA was a
double helix.
Diffraction X ray DNA
Watson and Crick
Watson & Crick won a Nobel Prize for
discovering the structural model of
DNA.
Watson and Crick
They credited Wilkins
and Franklin.
Wilkins also got a
Nobel Prize but
Franklin did not.
Franklin had passed
away and the Nobels
are not awarded
posthumously.
lipids
Nucleic
acids
Proteins
carbohydrates
DNA is a Nucleic Acid
What is a nucleic acid?
Nucleic acids are one of the major
organic compounds.
DNA
DNA Structure
What is the monomer for nucleic acids?
What is the structure of this monomer?
nucleotide
phosphate
sugar
nitrogen base
PO4
N base
Sugar
Deoxyribose
A NUCLEOTIDE
1. Phosphate Group
3. 5-Carbon
2.
Nitrogen Base
Sugar
2. 5-Carbon Sugar
1. Phosphate Group
(Dexoyribose or Ribose)
(Dexoyribose or Ribose)
3.
1.
3. Nitrogen Base
2.
O
O
P
O
3.
1.
2.
O
C H2
C H3
C
O
CH
HC
C H CH
HO H O
Nucleotides, too
O
C
CH
N
N
C
O
H
Nucleotides
There are four nitrogen bases making
up four different nucleotides.
Purines
Adenine
A
Guanine
G
N base
Pyrimidines
Thymine T
Cytosine C
Chargaff’s Base Pair Rules
Adenine always bonds with thymine.
Adenine (A) to Thymine (T)
A
T
The lines between the bases represent hydrogen bonds
G
C
Guanine always bonds with Cytosine.
Guanine (G) to Cytosine (C)
Pairing DNA Nucleotides
What would
is the
a nucleotide?
base
be the
pairing
complementary
rule?
nucleotide pairing?
Nucleotide
P
S
N-b
C
G
Rule
A
A to T
A
C to G
T
G
DNA DOUBLE HELIX
5’End
3’End
ladder
shaped
molecule
Antiparallel
structure
3’End
5’End
Purpose of DNA
Why do we have DNA?
DNA contains our genetic
information
Where is it stored?
In the nucleus of a
eukaryotic cell.
In the nucleoid region of a
prokaryotic cell.
TRY THIS!
Using the base pairing rules, match
up the corresponding bases to this
segment of DNA.
DNA left strand: ACTTAGGCGTCA
DNA right strand: ?
TRY THIS!
Answer:
DNA left strand: ACTTAGGCGTCA
DNA right strand:TGAATCCGCAGT