Post on 19-Jan-2016
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DNADNAThe History and Structure of DNA
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’tfigured out
how thishappens
Frederick Griffith
Griffith was working on a vaccine for Streptococcus pneumoniaeHe worked with 2 strains of the bacteria:A disease causing a strain
which grew in smooth colonies
A harmless grain 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 R+ dead S
Bacteria
Live Smooth Bacteria
Live Rough Bacteria
Dead Smooth Bacteria
Griffith Proved:That somehow the dead bacteria have passed their disease-causing substanct to the harmless, living bacteria. We now know this as “transformation”.
Griffith discovered that transformation could transform harmless bacteria into disease-causing bacteria
DNA
This substance was later determined to be DNA!
Erwin Chargaff
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
A AA AA A
AT
T
T
T TT
T
CCC G G
G
Rosalind Franklin &Maurice Wilkins
Franklin and Wilkins used x-ray to discover that DNA was a double helix.
Rosalind Franklin
Diffraction X ray DNA
Watson and CrickWatson & Crick won a Nobel Prize for discovering the structural model of DNA.
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.
Watson and Crick
TRY THIS!
For each scientist write one word or phrase that describes their contribution to discovering DNA.
Griffith-
Chargaff-
Franklin-
Watson and Crick-
lipids
lipids
carbohydratescarbohydrates
Nucleic acids
Nucleic acids
ProteinsProteins
DNA is a Nucleic AcidWhat is a nucleic acid?
Nucleic acids are one of the major organic compounds.
DNA
DNA StructureWhat is the monomer for nucleic acids?
What is the structure of this monomer?
phosphatenucleotide
N base
PO4
SugarSugar
PO4
N base
sugarnitrogen base
A NUCLEOTIDE
H
H2
H H
H3
HH H
H
H
O
O
O
C C
C
N
N
PO
O
O
C
C
C C
C
O
OO
C
C
1.
2.
3.
1.
2.
3.
1. Phosphate Group2. 5-Carbon Sugar
(Dexoyribose or Ribose)3. Nitrogen Base
1. Phosphate Group
2. 5-Carbon Sugar(Dexoyribose or Ribose)
3. Nitrogen Base
Nucleotides, too
NucleotidesThere are four nitrogen bases making up four different nucleotides.
Adenine
Guanine
Thymine
CytosinePyrimidines
PurinesA
C
G
T
N base
Chargaff’s Base Pair RulesAdenine always bonds with thymine.
Adenine (A) to Thymine (T)
Guanine always bonds with Cytosine.
Guanine (G) to Cytosine (C)
The lines between the bases represent hydrogen bonds
A
CG
T
C
G
A
A
T
G
Nucleotide
PS
N-b
Pairing DNA NucleotidesWhat is a nucleotide?
Rule
A to
C to
T
G
What is the base pairing rule?What would be the complementary nucleotide pairing?
3’End
3’End 5’End
5’End
DN
A D
OU
BL
E H
EL
IX
ladder shaped molecule
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: TGAACCGCAGT