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The Molecular Basis of Genetics
Chapter 10: DNA Structure and Analysis
The flow of information:
1. Storage
2. Replication
3. Expression
DNA as the Genetic Material
Historically:
*1868 Friedrick Miescher
*1910 Phoebus Levene
tetranucleotide hypothesis
*1927 Frederick Griffith
transforming principle
*1944 Avery, MacLeod and McCarty
*1952 Alfred Hershey and Martha Chase
Evidence for DNA in Eukaryotes:
Indirect evidence:
*Distribution of DNA
*Mutagenesis
Organism
Human
n
2n
3.25
7.30
Chicken
1.26
2.49
Trout
2 67
2.67
5 79
5.79
*RNA – genetic material in
some viruses
1
Nucleotide Structure: Pentose sugar
Nucleotide Structure: Nitrogenous Bases
Structural Analysis of DNA:
*nucleoside
*nucleotide
2
Nucleic Acid Polarity
*Top of molecule has
free 5’-phosphate group
This is the 5’ end
*Bottom has a free 3’
hydroxyl group
This is the 3’ end
Base Composition:
*1949-1953 Chargaff’s Rules
Source
A
T
G
C
A/T
G/C
A+G/C+T
Human
30.9
29.4
19.9
19.8
1.05
1.00
1.04
A+T/C+G
1.52
Sea Urchin
32.8
32.1
17.7
17.3
1.02
1.02
1.02
1.58
E. coli
24.7
23.6
26.0
25.7
1.04
1.01
1.03
0.93
T7
26.0
26.0
24.0
24.0
1.00
1.00
1.00
1.08
Organism
%
%G+C
Phage T2
36.0
Drosophila
45.0
Maize
49.1
Euglena
53.5
Neurospora
53.7
Complementarity
3
DNA Structure:
*Early 1950’s Rosalind Franklin
*1953 Watson and Crick
*Linus Pauling
RNA Structure:
*Similar to DNA except:
*Three major classes of RNA
S.R. Eddy (2001) Noncoding RNA genes and the modern RNA
world, Nature Reviews Genetics, 2:919-929
4
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