1. DNA (Deoxyribonucleic Acid)

2. DNA is made up of repeating molecules called NUCLEOTIDES.
Phosphate
Group N
Nitrogenous base
(A, G, C, or T)
CH2 O C1 C4 C3 C2 5
Sugar
(deoxyribose)

3. Watson & Crick proposed…
DNA had specific pairing between the nitrogen bases:
ADENINE – THYMINE
CYTOSINE – GUANINE
DNA is made of 2 long strands of nucleotides arranged in a specific way called the “Complementary Base-Pair Rule”

4. DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone

5. Nitrogenous Bases PURINES 1. Adenine (A) 2. Guanine (G) PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
A or G
T or C

6. Chargaff’s Rule Adenine must pair with Thymine
Guanine must pair with Cytosine
Their amounts in a given DNA molecule will be about the same.
H-bonds T A G C

7. (1961) Watson & Crick proposed…
…DNA controlled cell function by serving as a template for PROTEIN structure
3 Nucleotides = a triplet or CODON
(which code for a specific AMINO ACID)
AMINO ACIDS are the building blocks of PROTEINS

8. DNA Double Helix P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A