Section 2: Structure of DNA
Function: Stores and transmits genetic information.
Structure:
• Type of organic macromolecule = nucleic acid
• Polymer = polynucleotide
• Monomer = nucleotide
Each nucleotide contains 3 parts:
1. Sugar (deoxyribose)
2. Phosphate group
3. Nitrogen-containing base
Phoebus Levene
Studied composition of DNA in the early 1900’s
Determined it was made up of three basic pieces
Structure of DNA
DNA has 4 different nitrogenous bases
What is the structural difference between purine and
pyrimidine bases.
Chargaff
• Analyzed the percentage of each
base in a strand of DNA.
• His results:
– The amount of adenine is equal
to the amount of thymine
– Cytosine is equal to guanine
– Why did he get these results?
Structure of DNA
Complimentary Base Pairing
• Adenine (A) always bonds with Thymine (T)
• Guanine (G) always bond with Cytosine (C)
Hydrogen Bonding
• What is a hydrogen bond?
• Hydrogen bonds hold the two
strands of the DNA molecule
together
• There are 3 bonds between C and G
• There are 2 bonds between A and T