DNA as Genetic Material
Genetics
Bio 36404
Transmission Genetics
Mendelian Genetics
Classical Genetics
P:
Round vs Wrinkled Peas
RR
rr
F1:
All Round
Rr
3/4 Round: 1/4 Wrinkled
1/4RR 2/4Rr
1/4rr
F2:
Cytological
Genetics
Chromosomes and
Abnormalities
Molecular Genetics
• Chemistry of the Gene
• What are genes made of?
• How do they result in traits?
• How are they replicated?
• How do we manipulate them?
Timeline
• 1866
• 1902
Mendel
Sutton - proposed genes on
chromosomes
• 1910
Morgan - sex-linked traits, verified
genes on chromosomes
• Chromosomes composed of DNA and
protein
1928 Griffith Experiment
Streptococcus pneumoniae
inject into mouse
S form - wild type
smooth colonies
mouse dies
1928 Griffith Experiment
inject into mouse
R form - rough colonies
mouse lives
1928 Griffith Experiment
Heat Killed S
inject into mouse
mouse lives
1928 Griffith Experiment
inject into mouse
mouse dies
live S forms
found in
tissue
Mixture of
Rough and
Heat-Killed S
Form
transformation
1944 Avery, MacLeod & McCarty
S
Centrifuge
Heat
Blender
1944 Avery, MacLeod & McCarty
protease
removes
protein
carbs
proteins
fats
DNA
RNA
RNAase
removes
RNA
carbs
fats
DNA
RNA
DNAase
removes
DNA
carbs
fats
DNA
carbs
fats
1944 Avery, MacLeod & McCarty
protease
removes
protein
DNAase
removes
DNA
RNAase
removes
RNA
Conclusion?
DNA
causes
transformation
R
transformation
R
transformation
R
no
transformation
1952
Hershey
& Chase
Bacteriophages bacterial viruses
Protein
DNA
Bacteria
Viruses attach to bacteria
1952
Hershey
& Chase
Bacteria
inject DNA
or protein?
new
viruses
grow
viruses
released
Bacteria
1952 Hershey & Chase
phage + E. coli
with radioactive P
phage with
radioactive DNA
phage + E.coli with
radioactive S
phage with
radioactive protein
1952 Hershey & Chase
radioactive phage
+ normal E. coli
radioactive phage
+normal E.coli
1952 Hershey & Chase
radioactive phage
+ normal E. coli
? ? ?
radioactive phage
+normal E.coli
? ? ?
Blender
1952 Hershey & Chase
Conclusion:
DNA enters cell
radioactive DNA phage
+ normal E. coli
? ? ?
Blender
radioactive
inside
1952 Hershey & Chase
Conclusion:
protein
does not
enter cell
radioactive protein phage
+normal E.coli
radioactive outside
? ? ?
Blender
DNA Chemistry
• DNA breaks down into 3 components
• Phosphate (phosphoric acid)
• Deoxyribose (sugar)
• Nitrogenous bases (4)
Phosphate PO4
O
O-
P
3-
O
O-
O
P
O
OP
O
Ribose and Deoxyribose
H
H
5’
H
C
C
H
O
4’
O
C
H
H
1’
H
H
3’C
C
O
O
H
H
C
2’
O
H
H
O
H
H
O
C
H
H
H
C
C
O
H
H
C
2’
O
H
Nitrogenous Base
• ring contains N & C
H
H
H
H
C
N
C
N
C
C
N
pyrimidine
H
H
C
C
N
C
C
C
N
N
H
purine
H
Bases
Pyrimidines
Cytosine
Thymine
CH3
NH2
O
O
O
Purines
Guanine
Adenine
O
NH2
NH2
Nucleotide
P
5’
Base
O
sugar
1’
Nucleotide Joining
P
Base
O
5’
sugar
1’
3’
P
5’
Base
O
sugar
1’
The End