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Foundations of Scientific Process
Classical Genetics
Chromosomes are highly condensed structures in the nucleus of every cell
built from DNA wrapped around series of histone proteins
Chromosomes are highly condensed structures in the nucleus of every cell
built from DNA wrapped around series of histone proteins
Genome
the complete package of
genetic material (all DNA) for
a living organism , organized
in 23 pairs of chromosomes
In humans the entire stretch of DNA
polymer is made of ~ 3·109 monomer units
Chromosomes are highly condensed structures in the nucleus of every cell
built from DNA wrapped around series of histone proteins
Genome
the complete package of
genetic material (all DNA) for
a living organism , organized
in 23 pairs of chromosomes
Gene is a stretch of DNA that contains the
instructions for making a protein
DNA segment that encodes
for a protein
when and where it is made
new definition of a Gene
Chemical Composition of Living Matter
small subset of atoms provides an
extensive molecular diversity
6 atomic constituents
C, H, N, O, P, S
build 99.6% of living matter
3 essential biomolecules for existence
and continuation of life:
DNA, RNA: 4 nucleic bases
Proteins: 20 amino acids
variable units
All life is based on 6 chemical elements that are arranged
in more complex structures (DNA, RNA, proteins)
Genetic code for DNA
2 strands of backbone
locked by base pairs
double helix
4 Nucleic Bases:
Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
Adenine
Guanine
Thymine
Cytosine
Genetic code for DNA
2 strands of backbone
locked by base pairs
double helix
4 Nucleic Bases:
Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
Thymine
Adenine
Pairing
A-T
G-C
Guanine
Cytosine
It is the wave
function that describes the particle's
H-bonding
interactions
motion
when it travels unobserved.
help
cross-link:
H-bonding  attractive force between one
electronegative atom (O,F, N) and a hydrogen
covalently bonded to another electronegative atom.
cross-linking via H-bonding
example:
Kevlar derives part of its high strength from intermolecular hydrogen bonds on neighboring
polymer chains and aromatic (ring) stacking
interactions between stacked strands
0.34 nm
The structure of DNA:
chemical variability
nucleic bases in arbitrary sequence
repetitive structure
• backbone
• uniform helix
base -sequence encodes the meaning
Notice that the widths of the
pairs A-T and G-C are equal
Watson and Crick
The structure of DNA:
chemical variability
nucleic bases in arbitrary sequence
repetitive structure
• backbone
• uniform helix
Notice that the widths of the
pairs A-T and G-C are equal
base -sequence encodes the meaning
Physically Repetitive, Chemically Variable
The structure of DNA:
chemical variability
nucleic bases in arbitrary sequence
repetitive structure
• backbone
• uniform helix
Notice that the widths of the
pairs A-T and G-C are equal
base -sequence encodes the meaning
Physically Repetitive, Chemically Variable
Why is this significant ?
The structure of DNA:
chemical variability
nucleic bases in arbitrary sequence
repetitive structure
• backbone
• uniform helix
Notice that the widths of the
pairs A-T and G-C are equal
base -sequence encodes the meaning
Physically Repetitive, Chemically Variable
 Readability requires some
sort of regular structure that can be
algorithmically sifted through
(semi-conservative replication)
 Chemically variability in sequence
provides a meaning and
a genetic diversity
Semi-conservative Replication: DNA  DNA
ONE
COPY
C
G
T
A
G
C
A
T
Sequence info is
kept by separated
strand
G
C
A
T
DNA polymerase
G
C
T
A
+ mix of four subunit bases
G
EXACT
COPY
TWO
COPIES
T
C
G
T
A
G
C
A
T
A
C
C
G
T
EXACT
COPY
A
Provides opportunity for
introduction and
preservation of Novelty
C
G
T
A
G
C
A
T
semi-conservative replication of DNA
Genetic code for RNA
1 strands of backbone
with base pairs
single helix
4 Nucleic Bases:
Adenine (A), Uracil (U), Guanine (G), and Cytosine (C)
Adenine
Guanine
Uracil
Cytosine
Triplet of RNA bases (codon) translates into a particular amino acids
Meaning of a genetic code
Proteins
What Is A Virus?: Genetics Review
The structure of DNA:
variable sequence (string) built of
20 amino acids (building blocks)
strings of amino acids fold up into
particular shape
Shape governs the Function (Meaning)
Hereditary Material:
Proteins (backbone + 20 amino acids)
DNA (backbone + 4 nucleic bases)
Protein vs. DNA
Hereditary Material:
Proteins (backbone + 20 amino acids)
DNA (backbone + 4 nucleic bases)
Protein vs. DNA
Hershey-Chase experiment:
Virus infects Bacteria
32P-labeled
DNA
35S-labeled
Protein
Hereditary Material:
Proteins (backbone + 20 amino acids)
DNA (backbone + 4 nucleic bases)
Protein vs. DNA
Hershey-Chase experiment:
2/3 within bacterium
Virus infects Bacteria
32P-labeled
DNA
35S-labeled
Protein
1/4 within bacterium
The Central Dogma of
Molecular Biology:
1) DNA encodes RNA
2) RNA encodes Proteins
3) Proteins encode shape/function
DNA  RNA  Protein
 Genetic information (the MEANING) is encoded in the
SEQUENCE of basis along the DNA strand;
 DNA is not a direct template for protein synthesis;
The History of Classical Genetics
NATURE|Vol 441|25 May 2006