Transcript DNA Structure powerpoint

DNA
(Deoxyribonucleic Acid)
Quick Review:
• What is a chromosome made of?
• What is the monomer of the DNA polymer?
• Why is DNA wrapped so tightly?
• How are DNA, proteins, and traits related?
SEE p. 292-293
• Discovery of the DNA double helix
A. Frederick Griffith – Discovers that a factor
in diseased bacteria can transform harmless
bacteria into deadly bacteria
(1928)
B. Rosalind Franklin - X-ray photo of DNA.
(1952)
C. Watson and Crick - described the
DNA molecule from Franklin’s X-ray.
(1953)
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone
DNA Nucleotide
Watson & Crick proposed…
•DNA had specific pairing between the
nitrogen bases:
ADENINE – THYMINE
CYTOSINE - GUANINE
•DNA was made of 2 long stands of
nucleotides arranged in a specific way
called the “Complementary Rule”
DNA Double Helix
5
O
3
Hydrogen
bond
3
O
P
5
O
C
G
1
P
5
3
2
4
4
2
3
1
P
T
5
A
P
3
O
O
P
5
O
3
5
P
Nitrogen Bases
• PURINES
1. Adenine (A)
2. Guanine (G)
A or G
• PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
T or C
H-bonds
G
T
C
A
Sugar-phosphate
backbone on outside.
Nitrogenous bases
on the inside of the
structure
•Adenine always binds with Thymine
•Cytosine always binds with Guanine
Purine with
pyrimidine
Genetic Diversity…
• Different
arrangements of
NUCLEOTIDES in a
nucleic acid (DNA)
provides the key to
DIVERSITY among
living organisms.
The Code of Life…
• The “code” of the chromosome is the
SPECIFIC ORDER that bases occur.
T
C
A
T
G
C…